Bump actions/checkout from 3 to 4 (#105)

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

.github/workflows/website.yml

@@ -36,7 +36,7 @@ jobs:
           python3 -m pip install --upgrade pip setuptools wheel pyyaml==5.3.1 requests
 
       - name: Checkout the lesson
-        uses: actions/checkout@v3
+        uses: actions/checkout@v4
         with:
           fetch-depth: 0
           ref: ${{ github.event.pull_request.head.sha }}
@@ -93,7 +93,7 @@ jobs:
 
       - name: Checkout github pages
         if: ${{ github.event_name == 'push' && steps.check-rmd.outputs.count != 0 && github.ref != 'refs/heads/gh-pages'}}
-        uses: actions/checkout@v3
+        uses: actions/checkout@v4
         with:
           ref: gh-pages
           path: gh-pages