Remove old link for java gradle incompatibility (#168561)

We don't need this link anymore, and the current instructions already
tell users what to do.

Fixes https://github.com/flutter/website/issues/11530

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we expect every widget to implement].
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above.
- [x] I updated/added relevant documentation (doc comments with `///`).
- [x] I added new tests to check the change I am making, or this PR is
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Fixes] where supported.
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Co-authored-by: Gray Mackall <mackall@google.com>

packages/flutter_tools/lib/src/android/gradle_errors.dart

@@ -578,9 +578,7 @@ final GradleHandledError incompatibleJavaAndGradleVersionsHandler = GradleHandle
     globals.printBox(
       "${globals.logger.terminal.warningMark} Your project's Gradle version "
       'is incompatible with the Java version that Flutter is using for Gradle.\n\n'
-      'If you recently upgraded Android Studio, consult the migration guide '
-      'at https://flutter.dev/to/java-gradle-incompatibility.\n\n'
-      'Otherwise, to fix this issue, first, check the Java version used by Flutter by '
+      'To fix this issue, first, check the Java version used by Flutter by '
       'running `flutter doctor --verbose`.\n\n'
       'Then, update the Gradle version specified in ${gradlePropertiesFile.path} '
       'to be compatible with that Java version. '

packages/flutter_tools/test/general.shard/android/gradle_errors_test.dart

@@ -1351,7 +1351,6 @@ Could not compile build file '…/example/android/build.gradle'.
           testLogger.statusText,
           contains('Gradle version is incompatible with the Java version'),
         );
-        expect(testLogger.statusText, contains('flutter.dev/to/java-gradle-incompatibility'));
         expect(testLogger.statusText, contains('gradle-wrapper.properties'));
         expect(
           testLogger.statusText,