Bump ruby/setup-ruby from 1.120.1 to 1.121.0

Bumps [ruby/setup-ruby](https://github.com/ruby/setup-ruby) from 1.120.1 to 1.121.0.
- [Release notes](https://github.com/ruby/setup-ruby/releases)
- [Commits](ruby/setup-ruby@f2c070b...8ddb7b3)

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

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]

.github/workflows/exercise-tests.yml

@@ -22,7 +22,7 @@ jobs:
       - uses: actions/checkout@v3
 
       - name: Set up Ruby
-        uses: ruby/setup-ruby@f2c070bbf74632495b403899c87610cd4cb99dbe
+        uses: ruby/setup-ruby@8ddb7b3348b3951590db24c346e94ebafdabc926
         with:
           ruby-version: ${{ matrix.ruby-version }}
           bundler-cache: true