Bump actions/checkout from 3 to 4 (#538)

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

.github/workflows/ci.yml

@@ -21,7 +21,7 @@ jobs:
           - rails_61
           - rails_70
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - name: Configure bundler (default)
         run: |
           echo "BUNDLE_GEMFILE=Gemfile" >> "$GITHUB_ENV"
@@ -50,7 +50,7 @@ jobs:
     needs:
       - test
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - uses: actions/download-artifact@v3
         with:
           name: coverage