fix(flutter): update Docker image for Flutter tests

The fischerscode/flutter-sudo Docker image has not been updated for 11 months so it doesn't have the latest Flutter SDK versions. This commit updates the Docker image to use `ghcr.io/cirruslabs/flutter` for both beta and stable channels, ensuring that the tests run with the latest Flutter SDK.

Author: stnguyen90

tests/FlutterBetaTest.php

@@ -16,7 +16,7 @@ class FlutterBetaTest extends Base
         'cp tests/languages/flutter/tests.dart tests/sdks/flutter/test/appwrite_test.dart',
     ];
     protected string $command =
-        'docker run --network="mockapi" --rm -v $(pwd):/app -w /app/tests/sdks/flutter fischerscode/flutter-sudo:beta sh -c "sudo chown -R flutter:flutter . && flutter pub get && flutter test test/appwrite_test.dart"';
+        'docker run --network="mockapi" --rm -v $(pwd):/app -w /app/tests/sdks/flutter ghcr.io/cirruslabs/flutter:beta sh -c "flutter pub get && flutter test test/appwrite_test.dart"';
 
     protected array $expectedOutput = [
         ...Base::PING_RESPONSE,

tests/FlutterStableTest.php

@@ -16,7 +16,7 @@ class FlutterStableTest extends Base
         'cp tests/languages/flutter/tests.dart tests/sdks/flutter/test/appwrite_test.dart',
     ];
     protected string $command =
-        'docker run --network="mockapi" --rm -v $(pwd):/app:rw -w /app/tests/sdks/flutter fischerscode/flutter-sudo:stable sh -c "sudo chown -R flutter:flutter . && flutter pub get && flutter test test/appwrite_test.dart"';
+        'docker run --network="mockapi" --rm -v $(pwd):/app:rw -w /app/tests/sdks/flutter ghcr.io/cirruslabs/flutter:stable sh -c "flutter pub get && flutter test test/appwrite_test.dart"';
 
     protected array $expectedOutput = [
         ...Base::PING_RESPONSE,