Bump active_model_serializers from 0.10.8 to 0.10.9 (mastodon#10018)

Bumps [active_model_serializers](https://github.com/rails-api/active_model_serializers) from 0.10.8 to 0.10.9.
- [Release notes](https://github.com/rails-api/active_model_serializers/releases)
- [Changelog](https://github.com/rails-api/active_model_serializers/blob/v0.10.9/CHANGELOG.md)
- [Commits](rails-api/active_model_serializers@v0.10.8...v0.10.9)

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

Gemfile.lock

@@ -38,7 +38,7 @@ GEM
       erubi (~> 1.4)
       rails-dom-testing (~> 2.0)
       rails-html-sanitizer (~> 1.0, >= 1.0.3)
-    active_model_serializers (0.10.8)
+    active_model_serializers (0.10.9)
       actionpack (>= 4.1, < 6)
       activemodel (>= 4.1, < 6)
       case_transform (>= 0.2)