Update several comments related to theme normalization (#179457)

## Description

This PR updates some comments in various widgets to reflect the changes
related to Theme normalization.

## Related Issue

Related to https://github.com/flutter/flutter/issues/91772

## Tests

- Documentation only

packages/flutter/lib/src/material/bottom_app_bar_theme.dart

@@ -16,7 +16,7 @@ import 'theme.dart';
 /// Defines default property values for descendant [BottomAppBar] widgets.
 ///
 /// Descendant widgets obtain the current [BottomAppBarThemeData] object using
-/// `[BottomAppBarTheme.of]`. Instances of [BottomAppBarThemeData] can be
+/// [BottomAppBarTheme.of]. Instances of [BottomAppBarThemeData] can be
 /// customized with [BottomAppBarThemeData.copyWith].
 ///
 /// Typically a [BottomAppBarThemeData] is specified as part of the overall [Theme]

packages/flutter/lib/src/material/bottom_navigation_bar_theme.dart

@@ -17,7 +17,7 @@ import 'theme.dart';
 /// widgets.
 ///
 /// Descendant widgets obtain the current [BottomNavigationBarThemeData] object
-/// using `BottomNavigationBarTheme.of(context)`. Instances of
+/// using [BottomNavigationBarTheme.of]. Instances of
 /// [BottomNavigationBarThemeData] can be customized with
 /// [BottomNavigationBarThemeData.copyWith].
 ///

packages/flutter/lib/src/material/card.dart

@@ -131,7 +131,7 @@ class Card extends StatelessWidget {
 
   /// The color to paint the shadow below the card.
   ///
-  /// If null then the ambient [CardTheme]'s shadowColor is used.
+  /// If null then the ambient [CardThemeData.shadowColor] is used.
   /// If that's null too, then the overall theme's [ThemeData.shadowColor]
   /// (default black) is used.
   final Color? shadowColor;
@@ -158,16 +158,16 @@ class Card extends StatelessWidget {
   ///
   /// Defines the card's [Material.elevation].
   ///
-  /// If this property is null then [CardTheme.elevation] of
-  /// [ThemeData.cardTheme] is used. If that's null, the default value is 1.0.
+  /// If this property is null then the ambient [CardThemeData.elevation] is
+  /// used. If that's null, the default value is 1.0.
   final double? elevation;
 
   /// The shape of the card's [Material].
   ///
   /// Defines the card's [Material.shape].
   ///
-  /// If this property is null then [CardTheme.shape] of [ThemeData.cardTheme]
-  /// is used. If that's null then the shape will be a [RoundedRectangleBorder]
+  /// If this property is null then the ambient [CardThemeData.shape] is used.
+  /// If that's null then the shape will be a [RoundedRectangleBorder]
   /// with a circular corner radius of 12.0 and if [ThemeData.useMaterial3] is
   /// false, then the circular corner radius will be 4.0.
   final ShapeBorder? shape;
@@ -180,17 +180,17 @@ class Card extends StatelessWidget {
 
   /// {@macro flutter.material.Material.clipBehavior}
   ///
-  /// If this property is null then [CardTheme.clipBehavior] of
-  /// [ThemeData.cardTheme] is used. If that's null then the behavior will be [Clip.none].
+  /// If this property is null then the ambient [CardThemeData.clipBehavior] is
+  /// used. If that's null then the behavior will be [Clip.none].
   final Clip? clipBehavior;
 
   /// The empty space that surrounds the card.
   ///
   /// Defines the card's outer [Container.margin].
   ///
-  /// If this property is null then [CardTheme.margin] of
-  /// [ThemeData.cardTheme] is used. If that's null, the default margin is 4.0
-  /// logical pixels on all sides: `EdgeInsets.all(4.0)`.
+  /// If this property is null then the ambient [CardThemeData.margin] is used.
+  /// If that's null, the default margin is 4.0 logical pixels on
+  /// all sides: `EdgeInsets.all(4.0)`.
   final EdgeInsetsGeometry? margin;
 
   /// Whether this widget represents a single semantic container, or if false

packages/flutter/lib/src/material/card_theme.dart

@@ -13,16 +13,19 @@ import 'package:flutter/widgets.dart';
 
 import 'theme.dart';
 
+// Examples can assume:
+// late BuildContext context;
+
 /// Defines default property values for descendant [Card] widgets.
 ///
-/// Descendant widgets obtain the current [CardTheme] object using
-/// `CardTheme.of(context)`. Instances of [CardTheme] can be
-/// customized with [CardTheme.copyWith].
+/// Descendant widgets obtain the current [CardThemeData] object using
+/// [CardTheme.of]. Instances of [CardThemeData] can be
+/// customized with [CardThemeData.copyWith].
 ///
-/// Typically a [CardTheme] is specified as part of the overall [Theme]
+/// Typically a [CardThemeData] is specified as part of the overall [Theme]
 /// with [ThemeData.cardTheme].
 ///
-/// All [CardTheme] properties are `null` by default. When null, the [Card]
+/// All [CardThemeData] properties are `null` by default. When null, the [Card]
 /// will use the values from [ThemeData] if they exist, otherwise it will
 /// provide its own defaults.
 ///
@@ -157,7 +160,15 @@ class CardTheme extends InheritedWidget with Diagnosticable {
     );
   }
 
-  /// The [ThemeData.cardTheme] property of the ambient [Theme].
+  /// Returns the configuration [data] from the closest [CardTheme] ancestor.
+  ///
+  /// If there is no ancestor, it returns [ThemeData.cardTheme].
+  ///
+  /// Typical usage is as follows:
+  ///
+  /// ```dart
+  /// CardThemeData theme = CardTheme.of(context);
+  /// ```
   static CardThemeData of(BuildContext context) {
     final CardTheme? cardTheme = context.dependOnInheritedWidgetOfExactType<CardTheme>();
     return cardTheme?.data ?? Theme.of(context).cardTheme;

packages/flutter/lib/src/material/checkbox.dart

@@ -352,7 +352,7 @@ class Checkbox extends StatefulWidget {
   /// The shape of the checkbox's [Material].
   /// {@endtemplate}
   ///
-  /// If this property is null then [CheckboxThemeData.shape] of [ThemeData.checkboxTheme]
+  /// If this property is null then the ambient [CheckboxThemeData.shape]
   /// is used. If that's null then the shape will be a [RoundedRectangleBorder]
   /// with a circular corner radius of 1.0 in Material 2, and 2.0 in Material 3.
   final OutlinedBorder? shape;
@@ -378,9 +378,8 @@ class Checkbox extends StatefulWidget {
   /// compatibility.
   /// {@endtemplate}
   ///
-  /// If this property is null, then [CheckboxThemeData.side] of
-  /// [ThemeData.checkboxTheme] is used. If that is also null, then the side
-  /// will be width 2.
+  /// If this property is null, then the ambient [CheckboxThemeData.side] is
+  /// used. If that is also null, then the side will be width 2.
   final BorderSide? side;
 
   /// {@template flutter.material.checkbox.isError}

packages/flutter/lib/src/material/checkbox_list_tile.dart

@@ -400,9 +400,8 @@ class CheckboxListTile extends StatelessWidget {
 
   /// Whether this list tile is intended to display three lines of text.
   ///
-  /// If null, the value from [ListTileThemeData.isThreeLine] is used.
-  /// If that is also null, the value from [ThemeData.listTileTheme] is used.
-  /// If still null, the default value is `false`.
+  /// If null then the ambient [ListTileThemeData.isThreeLine] is used.
+  /// If that is also null, the default value is `false`.
   final bool? isThreeLine;
 
   /// Whether this list tile is part of a vertically dense list.

packages/flutter/lib/src/material/checkbox_theme.dart

@@ -20,7 +20,7 @@ import 'theme_data.dart';
 /// Defines default property values for descendant [Checkbox] widgets.
 ///
 /// Descendant widgets obtain the current [CheckboxThemeData] object using
-/// `CheckboxTheme.of(context)`. Instances of [CheckboxThemeData] can be
+/// [CheckboxTheme.of]. Instances of [CheckboxThemeData] can be
 /// customized with [CheckboxThemeData.copyWith].
 ///
 /// Typically a [CheckboxThemeData] is specified as part of the overall [Theme]

packages/flutter/lib/src/material/data_table_theme.dart

@@ -19,9 +19,8 @@ import 'theme.dart';
 /// widgets.
 ///
 /// Descendant widgets obtain the current [DataTableThemeData] object
-/// using `DataTableTheme.of(context)`. Instances of
-/// [DataTableThemeData] can be customized with
-/// [DataTableThemeData.copyWith].
+/// using [DataTableTheme.of]. Instances of [DataTableThemeData] can
+/// be customized with [DataTableThemeData.copyWith].
 ///
 /// Typically a [DataTableThemeData] is specified as part of the
 /// overall [Theme] with [ThemeData.dataTableTheme].