Remove redundant useMaterial3: true (#163376)

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This PR removes redundant useMaterial3: true as described in
flutter/flutter#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.*

- flutter/flutter#162818

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---------

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

Author: 2shrestha22

dev/benchmarks/complex_layout/lib/src/app.dart

@@ -23,7 +23,7 @@ class ComplexLayoutAppState extends State<ComplexLayoutApp> {
   @override
   Widget build(BuildContext context) {
     return MaterialApp(
-      theme: lightTheme ? ThemeData.light() : ThemeData.dark(),
+      theme: lightTheme ? ThemeData() : ThemeData.dark(),
       title: 'Advanced Layout',
       home:
           scrollMode == ScrollMode.complex

dev/benchmarks/platform_views_layout/lib/main.dart

@@ -20,11 +20,7 @@ class PlatformViewApp extends StatefulWidget {
 class PlatformViewAppState extends State<PlatformViewApp> {
   @override
   Widget build(BuildContext context) {
-    return MaterialApp(
-      theme: ThemeData.light(),
-      title: 'Advanced Layout',
-      home: const PlatformViewLayout(),
-    );
+    return const MaterialApp(title: 'Advanced Layout', home: PlatformViewLayout());
   }
 }
 

dev/benchmarks/platform_views_layout/lib/main_ad_banners.dart

@@ -40,7 +40,6 @@ class PlatformViewAppState extends State<PlatformViewApp> {
   @override
   Widget build(BuildContext context) {
     return MaterialApp(
-      theme: ThemeData.light(),
       title: 'Advanced Layout',
       home: Scaffold(
         appBar: AppBar(title: const Text('Platform View Ad Banners')),

dev/benchmarks/platform_views_layout/lib/main_bottom_ad_banner.dart

@@ -44,7 +44,6 @@ class PlatformViewAppState extends State<PlatformViewApp> {
   @override
   Widget build(BuildContext context) {
     return MaterialApp(
-      theme: ThemeData.light(),
       title: 'Advanced Layout',
       home: Scaffold(
         appBar: AppBar(title: const Text('Platform View Bottom Ad Banner')),

dev/benchmarks/platform_views_layout/lib/main_hcpp.dart

@@ -22,11 +22,7 @@ class PlatformViewApp extends StatefulWidget {
 class PlatformViewAppState extends State<PlatformViewApp> {
   @override
   Widget build(BuildContext context) {
-    return MaterialApp(
-      theme: ThemeData.light(),
-      title: 'Advanced Layout',
-      home: const PlatformViewLayout(),
-    );
+    return const MaterialApp(title: 'Advanced Layout', home: PlatformViewLayout());
   }
 }
 

dev/benchmarks/platform_views_layout/lib/main_non_intersecting.dart

@@ -20,11 +20,7 @@ class PlatformViewApp extends StatefulWidget {
 class PlatformViewAppState extends State<PlatformViewApp> {
   @override
   Widget build(BuildContext context) {
-    return MaterialApp(
-      theme: ThemeData.light(),
-      title: 'Advanced Layout',
-      home: const PlatformViewLayout(),
-    );
+    return const MaterialApp(title: 'Advanced Layout', home: PlatformViewLayout());
   }
 }
 

dev/benchmarks/platform_views_layout_hybrid_composition/lib/main.dart

@@ -24,11 +24,7 @@ class PlatformViewApp extends StatefulWidget {
 class PlatformViewAppState extends State<PlatformViewApp> {
   @override
   Widget build(BuildContext context) {
-    return MaterialApp(
-      theme: ThemeData.light(),
-      title: 'Advanced Layout',
-      home: const PlatformViewLayout(),
-    );
+    return const MaterialApp(title: 'Advanced Layout', home: PlatformViewLayout());
   }
 }
 

dev/integration_tests/flutter_gallery/lib/demo/fortnightly/fortnightly.dart

@@ -176,7 +176,7 @@ over water meant for the whole central valley of California? The story will shoc
 final ThemeData _fortnightlyTheme = _buildFortnightlyTheme();
 
 ThemeData _buildFortnightlyTheme() {
-  final ThemeData base = ThemeData.light();
+  final ThemeData base = ThemeData();
   return base.copyWith(
     primaryTextTheme: _buildTextTheme(base.primaryTextTheme),
     scaffoldBackgroundColor: Colors.white,

dev/integration_tests/flutter_gallery/lib/demo/shrine/app.dart

@@ -81,7 +81,7 @@ IconThemeData _customIconTheme(IconThemeData original) {
 }
 
 ThemeData _buildShrineTheme() {
-  final ThemeData base = ThemeData.light();
+  final ThemeData base = ThemeData();
   return base.copyWith(
     colorScheme: kShrineColorScheme,
     primaryColor: kShrinePink100,

dev/integration_tests/new_gallery/lib/studies/crane/theme.dart

@@ -15,7 +15,7 @@ IconThemeData _customIconTheme(IconThemeData original, Color color) {
 }
 
 ThemeData _buildCraneTheme() {
-  final ThemeData base = ThemeData.light();
+  final ThemeData base = ThemeData();
 
   return base.copyWith(
     colorScheme: const ColorScheme.light().copyWith(