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/test.yml

@@ -36,7 +36,7 @@ jobs:
       BUNDLE_GEMFILE: ${{ matrix.gemfile }}
       JRUBY_OPTS: --debug
     steps:
-    - uses: actions/checkout@v3
+    - uses: actions/checkout@v4
     - name: Setup ImageMagick policy
       run: sudo sh -c 'echo '\''<policymap><policy domain="coder" rights="read|write" pattern="PDF" /></policymap>'\'' > /etc/ImageMagick-6/policy.xml'
     - name: Update package list
@@ -59,7 +59,7 @@ jobs:
     name: RuboCop
     runs-on: ubuntu-20.04
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - name: Set up Ruby
         uses: ruby/setup-ruby@v1
         with: