Bump flutter_lints from 4.0.0 to 6.0.0 in /packages/apidash_core

Bumps [flutter_lints](https://github.com/flutter/packages/tree/main/packages) from 4.0.0 to 6.0.0.
- [Commits](https://github.com/flutter/packages/commits/flutter_lints-v6.0.0/packages)

---
updated-dependencies:
- dependency-name: flutter_lints
  dependency-version: 6.0.0
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]

packages/apidash_core/pubspec.yaml

@@ -28,7 +28,7 @@ dev_dependencies:
   flutter_test:
     sdk: flutter
   build_runner: ^2.4.12
-  flutter_lints: ^4.0.0
+  flutter_lints: ^6.0.0
   freezed: ^2.5.7
   json_serializable: ^6.7.1
   test: ^1.25.2