Bump actions/checkout from 2 to 4 (#135)

Bumps [actions/checkout](https://github.com/actions/checkout) from 2 to 4.
- [Release notes](https://github.com/actions/checkout/releases)
- [Changelog](https://github.com/actions/checkout/blob/main/CHANGELOG.md)
- [Commits](actions/checkout@v2...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/release.yaml

@@ -15,7 +15,7 @@ jobs:
           package-name: rotp
           version-file: "lib/rotp/version.rb"
       # Checkout code if release was created
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v4
         if: ${{ steps.release.outputs.release_created }}
       # Setup ruby if a release was created
       - uses: ruby/setup-ruby@v1

.github/workflows/test.yaml

@@ -16,7 +16,7 @@ jobs:
         ruby-version: ['3.2', '3.0', '2.7', '2.3', truffleruby-head]
 
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - name: Set up Ruby ${{ matrix.ruby-version }}
         uses: ruby/setup-ruby@v1
         with: