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] <support@github.com>

.github/workflows/test.yml

@@ -17,7 +17,7 @@ jobs:
       - uses: jcs090218/setup-emacs@master
         with:
           version: ${{ matrix.emacs-version }}
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v4
       - uses: emacs-eldev/setup-eldev@v1
       - run: make lint
       - run: make compile