Bump actions/checkout from 3 to 4 (#318)

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/tsfc-tests.yml

@@ -17,7 +17,7 @@ jobs:
       CXX: g++-10
 
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - name: Set up Python
         uses: actions/setup-python@v5
         with:
@@ -28,7 +28,7 @@ jobs:
           pip3 install .
 
       - name: Clone tsfc
-        uses: actions/checkout@v3
+        uses: actions/checkout@v4
         with:
           path: ./tsfc
           repository: firedrakeproject/tsfc