build(deps): 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] <[email protected]>

.github/workflows/jekyll.yml

@@ -9,7 +9,7 @@ jobs:
     if: github.repository_owner == 'music-encoding'
 
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
 
       # Use GitHub Actions' cache to shorten build times and decrease load on servers
       - uses: actions/cache@v3

.github/workflows/link-checker.yml

@@ -39,7 +39,7 @@ jobs:
             echo "CHECK_BRANCH=${{ github.event.inputs.branch }}" >> $GITHUB_ENV
           fi
       - name: Checkout main repo
-        uses: actions/checkout@v3
+        uses: actions/checkout@v4
         with:
           ref: ${{ env.CHECK_BRANCH }}