Bump actions/checkout from 2 to 4

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]>

Author: dependabot[bot]

.github/workflows/generate.yml

@@ -17,11 +17,11 @@ jobs:
           sudo apt-get -y install libfuse2
           echo "LD_PRELOAD=/lib/x86_64-linux-gnu/libgmodule-2.0.so" >> $GITHUB_ENV
       - name: checkout master
-        uses: actions/checkout@v2
+        uses: actions/checkout@v4
         with:
           path: work
       - name: Checkout gh-pages
-        uses: actions/checkout@v2
+        uses: actions/checkout@v4
         with:
           path: target
           ref: gh-pages