Bump ruby/setup-ruby from 1.187.0 to 1.188.0 (#1709)

Bumps [ruby/setup-ruby](https://github.com/ruby/setup-ruby) from 1.187.0 to 1.188.0.
- [Release notes](https://github.com/ruby/setup-ruby/releases)
- [Changelog](https://github.com/ruby/setup-ruby/blob/master/release.rb)
- [Commits](ruby/setup-ruby@161cd54...50ba338)

---
updated-dependencies:
- dependency-name: ruby/setup-ruby
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

.github/workflows/exercise-tests.yml

@@ -22,7 +22,7 @@ jobs:
       - uses: actions/checkout@692973e3d937129bcbf40652eb9f2f61becf3332
 
       - name: Set up Ruby
-        uses: ruby/setup-ruby@161cd54b698f1fb3ea539faab2e036d409550e3c
+        uses: ruby/setup-ruby@50ba3386b050ad5b97a41fcb81240cbee1d1821f
         with:
           ruby-version: ${{ matrix.ruby-version }}
           bundler-cache: true