Add network permissions information to the dart doc of network image. (#167110)

Fixes https://github.com/flutter/flutter/issues/167103 (really it
documents the mistake someone can make)

## Pre-launch Checklist

- [x] I read the [Contributor Guide] and followed the process outlined
there for submitting PRs.
- [x] I read the [Tree Hygiene] wiki page, which explains my
responsibilities.
- [x] I read and followed the [Flutter Style Guide], including [Features
we expect every widget to implement].
- [x] I signed the [CLA].
- [x] I listed at least one issue that this PR fixes in the description
above.
- [x] I updated/added relevant documentation (doc comments with `///`).
- [ ] I added new tests to check the change I am making, or this PR is
[test-exempt].
- [x] I followed the [breaking change policy] and added [Data Driven
Fixes] where supported.
- [x] All existing and new tests are passing.

packages/flutter/lib/src/widgets/image.dart

@@ -421,6 +421,12 @@ class Image extends StatefulWidget {
   ///    [repeat], filtering, and blurring.
   ///
   /// By default, this feature is turned off ([WebHtmlElementStrategy.never]).
+  ///
+  /// ### Android Permissions
+  ///
+  /// Images fetched from the network require the internet permission.
+  /// Ensure that all AndroidMainifest.xml variants (especially release) have the internet permission.
+  /// See https://docs.flutter.dev/data-and-backend/networking for more information.
   Image.network(
     String src, {
     super.key,