chore(deps): Bump the built_value_generator group

Bumps the built_value_generator group in /packages/test/amplify_integration_test with 1 update: [built_value_generator](https://github.com/google/built_value.dart).


Updates `built_value_generator` from 8.8.1 to 8.9.1
- [Release notes](https://github.com/google/built_value.dart/releases)
- [Changelog](https://github.com/google/built_value.dart/blob/master/CHANGELOG.md)
- [Commits](https://github.com/google/built_value.dart/commits/v8.9.1)

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

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

Author: dependabot[bot]

packages/test/amplify_integration_test/pubspec.yaml

@@ -26,4 +26,4 @@ dependencies:
 dev_dependencies:
   amplify_lints: ^2.0.0
   build_runner: ^2.4.0
-  built_value_generator: 8.8.1
+  built_value_generator: 8.9.1