ci(deps): bump actions/checkout from 2 to 4 (#45)

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

.github/workflows/ci.yml

@@ -16,7 +16,7 @@ jobs:
     runs-on: ubuntu-latest
     continue-on-error: ${{ endsWith(matrix.ruby, 'head') || matrix.ruby == 'debug' }}
     steps:
-    - uses: actions/checkout@v2
+    - uses: actions/checkout@v4
     - run: rm Gemfile.lock
     - name: Setup Ruby ${{ matrix.ruby }}
       uses: ruby/setup-ruby@v1
@@ -64,7 +64,7 @@ jobs:
   lint:
     runs-on: ubuntu-latest
     steps:
-    - uses: actions/checkout@v2
+    - uses: actions/checkout@v4
     - uses: ruby/setup-ruby@v1
       with:
         bundler-cache: true
@@ -78,7 +78,7 @@ jobs:
   docs:
     runs-on: ubuntu-latest
     steps:
-    - uses: actions/checkout@v2
+    - uses: actions/checkout@v4
     - name: Check markdown files for broken links
       uses: justinbeckwith/linkinator-action@v1
       with: