chore(deps): bump json_serializable

Bumps the json_serializable group in /packages/amplify/amplify_flutter with 1 update: [json_serializable](https://github.com/google/json_serializable.dart).


Updates `json_serializable` from 6.9.5 to 6.10.0
- [Release notes](https://github.com/google/json_serializable.dart/releases)
- [Commits](google/json_serializable.dart@json_serializable-v6.9.5...json_serializable-v6.10.0)

---
updated-dependencies:
- dependency-name: json_serializable
  dependency-version: 6.10.0
  dependency-type: direct:production
  update-type: version-update:semver-minor
  dependency-group: json_serializable
...

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

packages/amplify/amplify_flutter/pubspec.yaml

@@ -34,4 +34,4 @@ dev_dependencies:
   build_runner: ^2.4.9
   flutter_test:
     sdk: flutter
-  json_serializable: ">=6.9.4 <6.10.0"
+  json_serializable: ^6.9.4