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/ci.yml

@@ -16,7 +16,7 @@ jobs:
       USE_GEM_PATCHED_LOCALLY: ${{ matrix.frozen_string_literal }}
 
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
         with:
           fetch-depth: 0
 
@@ -27,14 +27,14 @@ jobs:
           echo "RGGEN_BRANCH=${GITHUB_REF#refs/heads/}" >> ${GITHUB_ENV}
 
       - name: Checkout RgGen devtools
-        uses: actions/checkout@v3
+        uses: actions/checkout@v4
         with:
           repository: rggen/rggen-devtools
           path: rggen-devtools
           fetch-depth: 0
 
       - name: Checkout RgGen library list
-        uses: actions/checkout@v3
+        uses: actions/checkout@v4
         with:
           repository: rggen/rggen-checkout
           path: rggen-checkout