Bump actions/checkout from 3 to 4

Bumps [actions/checkout](https://github.com/actions/checkout) from 3 to 4.
- [Release notes](https://github.com/actions/checkout/releases)
- [Changelog](https://github.com/actions/checkout/blob/main/CHANGELOG.md)
- [Commits](actions/checkout@v3...v4)

---
updated-dependencies:
- dependency-name: actions/checkout
  dependency-type: direct:production
  update-type: version-update:semver-major
...

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

.github/workflows/ci.yml

@@ -23,7 +23,7 @@ jobs:
       BUNDLE_GEMFILE: gemfiles/${{ matrix.gemfile }}.gemfile
     steps:
       # https://github.com/marketplace/actions/checkout
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       # https://github.com/marketplace/actions/setup-ruby-jruby-and-truffleruby
       - name: Set up Ruby
         uses: ruby/setup-ruby@v1