Downgrade flutter_lints to 5.0.0 for CI compatibility

- flutter_lints 6.0.0 requires Dart SDK ^3.8.0
- Flutter 3.27.1 ships with Dart 3.6.0
- Downgrade to flutter_lints 5.0.0 for compatibility
- All tests still passing (118/118)

Author: anilcancakir

pubspec.yaml

@@ -24,7 +24,7 @@ dependencies:
 dev_dependencies:
   flutter_test:
     sdk: flutter
-  flutter_lints: ^6.0.0
+  flutter_lints: ^5.0.0
 
 executables:
   magic: magic