Bump rubocop-rails from 2.12.3 to 2.12.4 (#16869)

Bumps [rubocop-rails](https://github.com/rubocop/rubocop-rails) from 2.12.3 to 2.12.4.
- [Release notes](https://github.com/rubocop/rubocop-rails/releases)
- [Changelog](https://github.com/rubocop/rubocop-rails/blob/master/CHANGELOG.md)
- [Commits](https://github.com/rubocop/rubocop-rails/compare/v2.12.3...v2.12.4)

---
updated-dependencies:
- dependency-name: rubocop-rails
  dependency-type: direct:development
  update-type: version-update:semver-patch
...

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

Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Gemfile.lock

@@ -528,7 +528,7 @@ GEM
       unicode-display_width (>= 1.4.0, < 3.0)
     rubocop-ast (1.12.0)
       parser (>= 3.0.1.1)
-    rubocop-rails (2.12.3)
+    rubocop-rails (2.12.4)
       activesupport (>= 4.2.0)
       rack (>= 1.1)
       rubocop (>= 1.7.0, < 2.0)