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] <support@github.com>

.github/workflows/coq.yml

@@ -25,7 +25,7 @@ jobs:
     name: ${{ matrix.env.COQ_VERSION }}
 
     steps:
-    - uses: actions/checkout@v3
+    - uses: actions/checkout@v4
       with:
         submodules: recursive
     - name: install Coq

.github/workflows/update-tested.yml

@@ -11,7 +11,7 @@ jobs:
     runs-on: ubuntu-latest
     name: Update tested
     steps:
-    - uses: actions/checkout@v3
+    - uses: actions/checkout@v4
       with:
         ref: 'tested'
         fetch-depth: 0