chore(codelabs): remove redundant useMaterial3 flag (#2283)

This PR removes redundant occurrences of `useMaterial3: true` in Flutter
codelabs. Since `useMaterial3: true` is now the default, explicitly
setting it is unnecessary unless demonstrating its behavior. This change
helps keep the sample code clean and aligned with current Flutter
defaults.

Partial fix for
[flutter/flutter#162818](flutter/flutter#162818)

## Pre-launch Checklist

- [x] I read the [Effective Dart: Style] _recently_, and have followed
its advice.
- [x] I signed the [CLA].
- [x] I updated/added relevant documentation (doc comments with `///`).
- [ ] All existing and new tests are passing.

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

<!-- Links -->
[Effective Dart: Style]:
https://dart.dev/guides/language/effective-dart/style
[CLA]: https://cla.developers.google.com/
[Discord]:
https://github.com/flutter/flutter/blob/master/docs/contributing/Chat.md

---------

Co-authored-by: Brett Morgan <brett.morgan@gmail.com>

adaptive_app/codelab_rebuild.yaml

@@ -334,11 +334,9 @@ steps:
                 title: 'FlutterDev Playlists',
                 theme: FlexColorScheme.light(
                   scheme: FlexScheme.red,
-                  useMaterial3: true,
                 ).toTheme,
                 darkTheme: FlexColorScheme.dark(
                   scheme: FlexScheme.red,
-                  useMaterial3: true,
                 ).toTheme,
                 themeMode: ThemeMode.dark, // Or ThemeMode.System if you'd prefer
                 debugShowCheckedModeBanner: false,
@@ -1586,7 +1584,7 @@ steps:
           +      title: 'Your Playlists',
                  theme: FlexColorScheme.light(
                    scheme: FlexScheme.red,
-                   useMaterial3: true,
+                 ).toTheme,
       - name: Patch lib/src/adaptive_playlists.dart
         path: adaptive_app/lib/src/adaptive_playlists.dart
         patch-u: |

adaptive_app/step_03/macos/Runner/Configs/AppInfo.xcconfig

@@ -11,4 +11,4 @@ PRODUCT_NAME = adaptive_app
 PRODUCT_BUNDLE_IDENTIFIER = com.example.adaptiveApp
 
 // The copyright displayed in application information
-PRODUCT_COPYRIGHT = Copyright © 2024 com.example. All rights reserved.
+PRODUCT_COPYRIGHT = Copyright © 2025 com.example. All rights reserved.

adaptive_app/step_03/pubspec.yaml

@@ -19,7 +19,7 @@ publish_to: 'none' # Remove this line if you wish to publish to pub.dev
 version: 1.0.0+1
 
 environment:
-  sdk: ^3.6.0-0
+  sdk: ^3.6.2
 
 # Dependencies specify other packages that your package needs in order to work.
 # To automatically upgrade your package dependencies to the latest versions

adaptive_app/step_03/windows/runner/Runner.rc

@@ -93,7 +93,7 @@ BEGIN
             VALUE "FileDescription", "adaptive_app" "\0"
             VALUE "FileVersion", VERSION_AS_STRING "\0"
             VALUE "InternalName", "adaptive_app" "\0"
-            VALUE "LegalCopyright", "Copyright (C) 2024 com.example. All rights reserved." "\0"
+            VALUE "LegalCopyright", "Copyright (C) 2025 com.example. All rights reserved." "\0"
             VALUE "OriginalFilename", "adaptive_app.exe" "\0"
             VALUE "ProductName", "adaptive_app" "\0"
             VALUE "ProductVersion", VERSION_AS_STRING "\0"

adaptive_app/step_04/lib/main.dart

@@ -67,11 +67,9 @@ class PlaylistsApp extends StatelessWidget {
       title: 'FlutterDev Playlists',
       theme: FlexColorScheme.light(
         scheme: FlexScheme.red,
-        useMaterial3: true,
       ).toTheme,
       darkTheme: FlexColorScheme.dark(
         scheme: FlexScheme.red,
-        useMaterial3: true,
       ).toTheme,
       themeMode: ThemeMode.dark, // Or ThemeMode.System if you'd prefer
       debugShowCheckedModeBanner: false,

adaptive_app/step_04/macos/Runner/Configs/AppInfo.xcconfig

@@ -11,4 +11,4 @@ PRODUCT_NAME = adaptive_app
 PRODUCT_BUNDLE_IDENTIFIER = com.example.adaptiveApp
 
 // The copyright displayed in application information
-PRODUCT_COPYRIGHT = Copyright © 2024 com.example. All rights reserved.
+PRODUCT_COPYRIGHT = Copyright © 2025 com.example. All rights reserved.

adaptive_app/step_04/pubspec.yaml

@@ -19,7 +19,7 @@ publish_to: 'none' # Remove this line if you wish to publish to pub.dev
 version: 1.0.0+1
 
 environment:
-  sdk: ^3.6.0-0
+  sdk: ^3.6.2
 
 # Dependencies specify other packages that your package needs in order to work.
 # To automatically upgrade your package dependencies to the latest versions
@@ -35,11 +35,11 @@ dependencies:
   # Use with the CupertinoIcons class for iOS style icons.
   cupertino_icons: ^1.0.8
   googleapis: ^13.2.0
-  http: ^1.2.2
+  http: ^1.3.0
   provider: ^6.1.2
   url_launcher: ^6.3.1
-  flex_color_scheme: ^8.0.0
-  go_router: ^14.4.1
+  flex_color_scheme: ^8.1.0
+  go_router: ^14.7.2
 
 dev_dependencies:
   flutter_test:

adaptive_app/step_04/windows/runner/Runner.rc

@@ -93,7 +93,7 @@ BEGIN
             VALUE "FileDescription", "adaptive_app" "\0"
             VALUE "FileVersion", VERSION_AS_STRING "\0"
             VALUE "InternalName", "adaptive_app" "\0"
-            VALUE "LegalCopyright", "Copyright (C) 2024 com.example. All rights reserved." "\0"
+            VALUE "LegalCopyright", "Copyright (C) 2025 com.example. All rights reserved." "\0"
             VALUE "OriginalFilename", "adaptive_app.exe" "\0"
             VALUE "ProductName", "adaptive_app" "\0"
             VALUE "ProductVersion", VERSION_AS_STRING "\0"

adaptive_app/step_05/lib/main.dart

@@ -70,11 +70,9 @@ class PlaylistsApp extends StatelessWidget {
       title: 'FlutterDev Playlists',
       theme: FlexColorScheme.light(
         scheme: FlexScheme.red,
-        useMaterial3: true,
       ).toTheme,
       darkTheme: FlexColorScheme.dark(
         scheme: FlexScheme.red,
-        useMaterial3: true,
       ).toTheme,
       themeMode: ThemeMode.dark, // Or ThemeMode.System if you'd prefer
       debugShowCheckedModeBanner: false,