Remove redundant useMaterial3: true (#163376)

<!--
Thanks for filing a pull request!
Reviewers are typically assigned within a week of filing a request.
To learn more about code review, see our documentation on Tree Hygiene:
https://github.com/flutter/flutter/blob/main/docs/contributing/Tree-hygiene.md
-->

This PR removes redundant useMaterial3: true as described in
https://github.com/flutter/flutter/issues/162818

*List which issues are fixed by this PR. You must list at least one
issue. An issue is not required if the PR fixes something trivial like a
typo.*

- https://github.com/flutter/flutter/issues/162818

## 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 `///`).
- [x] 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.
- [ ] All existing and new tests are passing.

If you need help, consider asking for advice on the #hackers-new channel
on [Discord].

<!-- Links -->
[Contributor Guide]:
https://github.com/flutter/flutter/blob/main/docs/contributing/Tree-hygiene.md#overview
[Tree Hygiene]:
https://github.com/flutter/flutter/blob/main/docs/contributing/Tree-hygiene.md
[test-exempt]:
https://github.com/flutter/flutter/blob/main/docs/contributing/Tree-hygiene.md#tests
[Flutter Style Guide]:
https://github.com/flutter/flutter/blob/main/docs/contributing/Style-guide-for-Flutter-repo.md
[Features we expect every widget to implement]:
https://github.com/flutter/flutter/blob/main/docs/contributing/Style-guide-for-Flutter-repo.md#features-we-expect-every-widget-to-implement
[CLA]: https://cla.developers.google.com/
[flutter/tests]: https://github.com/flutter/tests
[breaking change policy]:
https://github.com/flutter/flutter/blob/main/docs/contributing/Tree-hygiene.md#handling-breaking-changes
[Discord]:
https://github.com/flutter/flutter/blob/main/docs/contributing/Chat.md
[Data Driven Fixes]:
https://github.com/flutter/flutter/blob/main/docs/contributing/Data-driven-Fixes.md

---------

Co-authored-by: Qun Cheng <36861262+QuncCccccc@users.noreply.github.com>

packages/flutter_localizations/test/basics_test.dart

@@ -11,7 +11,6 @@ void main() {
     await tester.pumpWidget(
       MaterialApp(
         // Creates the outer Localizations widget.
-        theme: ThemeData(useMaterial3: true),
         home: ListView(
           children: <Widget>[
             const LocalizationTracker(key: ValueKey<String>('outer')),

packages/flutter_localizations/test/material/date_picker_test.dart

@@ -154,7 +154,6 @@ void main() {
   testWidgets('Material3 - locale parameter overrides ambient locale', (WidgetTester tester) async {
     Widget buildFrame() {
       return MaterialApp(
-        theme: ThemeData(useMaterial3: true),
         locale: const Locale('en', 'US'),
         supportedLocales: const <Locale>[Locale('en', 'US'), Locale('fr', 'CA')],
         localizationsDelegates: GlobalMaterialLocalizations.delegates,
@@ -235,7 +234,6 @@ void main() {
   ) async {
     Widget buildFrame() {
       return MaterialApp(
-        theme: ThemeData(useMaterial3: true),
         locale: const Locale('en', 'US'),
         home: Material(
           child: Builder(
@@ -318,7 +316,6 @@ void main() {
   ) async {
     Widget buildFrame() {
       return MaterialApp(
-        theme: ThemeData(useMaterial3: true),
         locale: const Locale('en', 'US'),
         supportedLocales: const <Locale>[Locale('en', 'US'), Locale('fr', 'CA')],
         localizationsDelegates: GlobalMaterialLocalizations.delegates,

packages/flutter_localizations/test/text_test.dart

@@ -82,7 +82,6 @@ void main() {
     final Key targetKey = UniqueKey();
     await tester.pumpWidget(
       MaterialApp(
-        theme: ThemeData(useMaterial3: true),
         routes: <String, WidgetBuilder>{
           '/next': (BuildContext context) {
             return const Text('Next');
@@ -212,7 +211,6 @@ void main() {
     final Key targetKey = UniqueKey();
     await tester.pumpWidget(
       MaterialApp(
-        theme: ThemeData(useMaterial3: true),
         routes: <String, WidgetBuilder>{
           '/next': (BuildContext context) {
             return const Text('Next');