Bump actions/checkout from 6 to 7

Bumps [actions/checkout](https://github.com/actions/checkout) from 6 to 7.
- [Release notes](https://github.com/actions/checkout/releases)
- [Changelog](https://github.com/actions/checkout/blob/main/CHANGELOG.md)
- [Commits](https://github.com/actions/checkout/compare/v6...v7)

---
updated-dependencies:
- dependency-name: actions/checkout
  dependency-version: '7'
  dependency-type: direct:production
  update-type: version-update:semver-major
...

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

.github/workflows/ci.yml

@@ -19,7 +19,7 @@ jobs:
           - { ruby: 'head', allowed-failure: true }
     name: Test Ruby ${{ matrix.entry.ruby }}
     steps:
-      - uses: actions/checkout@v6
+      - uses: actions/checkout@v7
       - uses: ruby/setup-ruby@v1
         with:
           ruby-version: ${{ matrix.entry.ruby }}
@@ -33,7 +33,7 @@ jobs:
       contents: read
     name: RuboCop
     steps:
-      - uses: actions/checkout@v6
+      - uses: actions/checkout@v7
       - uses: ruby/setup-ruby@v1
         with:
           ruby-version: 4.0 # Specify the latest supported Ruby version.
@@ -46,7 +46,7 @@ jobs:
       contents: read
     name: YARD Documentation
     steps:
-      - uses: actions/checkout@v6
+      - uses: actions/checkout@v7
       - uses: ruby/setup-ruby@v1
         with:
           ruby-version: 4.0 # Specify the latest supported Ruby version.