Bump rubocop-rails from 2.8.0 to 2.8.1 (#10390)

* Bump rubocop-rails from 2.8.0 to 2.8.1

Bumps [rubocop-rails](https://github.com/rubocop-hq/rubocop-rails) from 2.8.0 to 2.8.1.
- [Release notes](https://github.com/rubocop-hq/rubocop-rails/releases)
- [Changelog](https://github.com/rubocop-hq/rubocop-rails/blob/master/CHANGELOG.md)
- [Commits](https://github.com/rubocop-hq/rubocop-rails/compare/v2.8.0...v2.8.1)

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

* Bump rubocop-rails from 2.8.0 to 2.8.1 (Update vendor/cache)

Co-authored-by: dependabot-preview[bot] <27856297+dependabot-preview[bot]@users.noreply.github.com>

Gemfile.lock

@@ -666,11 +666,11 @@ GEM
       rubocop-ast (>= 0.3.0, < 1.0)
       ruby-progressbar (~> 1.7)
       unicode-display_width (>= 1.4.0, < 2.0)
-    rubocop-ast (0.3.0)
+    rubocop-ast (0.4.2)
       parser (>= 2.7.1.4)
     rubocop-performance (1.8.0)
       rubocop (>= 0.87.0)
-    rubocop-rails (2.8.0)
+    rubocop-rails (2.8.1)
       activesupport (>= 4.2.0)
       rack (>= 1.1)
       rubocop (>= 0.87.0)