Bump json_serializable from 6.8.0 to 6.9.0

Bumps [json_serializable](https://github.com/google/json_serializable.dart) from 6.8.0 to 6.9.0.
- [Release notes](https://github.com/google/json_serializable.dart/releases)
- [Commits](https://github.com/google/json_serializable.dart/compare/json_serializable-v6.8.0...json_serializable-v6.9.0)

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

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

pubspec.lock

@@ -781,10 +781,10 @@ packages:
     dependency: "direct dev"
     description:
       name: json_serializable
-      sha256: ea1432d167339ea9b5bb153f0571d0039607a873d6e04e0117af043f14a1fd4b
+      sha256: c2fcb3920cf2b6ae6845954186420fca40bc0a8abcc84903b7801f17d7050d7c
       url: "https://pub.dev"
     source: hosted
-    version: "6.8.0"
+    version: "6.9.0"
   leak_tracker:
     dependency: transitive
     description:

pubspec.yaml

@@ -79,7 +79,7 @@ dev_dependencies:
   integration_test:
     sdk: flutter
   build_runner: ^2.4.13
-  json_serializable: ^6.8.0
+  json_serializable: ^6.9.0
   mockito: ^5.4.4
   network_image_mock: ^2.1.1
   flutter_lints: ^5.0.0