Bump actions/cache from 3 to 4

Bumps [actions/cache](https://github.com/actions/cache) from 3 to 4.
- [Release notes](https://github.com/actions/cache/releases)
- [Changelog](https://github.com/actions/cache/blob/main/RELEASES.md)
- [Commits](actions/cache@v3...v4)

---
updated-dependencies:
- dependency-name: actions/cache
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <support@github.com>

.github/workflows/coq-docker.yml

@@ -138,7 +138,7 @@ jobs:
       id: set-output-step
       run: echo "coq_image_name=${{ runner.os }}-docker-${{ hashFiles('image.tar') }}" >> $GITHUB_OUTPUT
     - name: Cache Docker image
-      uses: actions/cache@v3
+      uses: actions/cache@v4
       with:
         path: image.tar
         key: ${{ runner.os }}-docker-${{ hashFiles('image.tar') }}
@@ -170,7 +170,7 @@ jobs:
       with:
         submodules: recursive
     - name: Restore cached Docker image ${{ needs.build.outputs.coq_image_name }}
-      uses: actions/cache@v3
+      uses: actions/cache@v4
       with:
         path: image.tar
         key: ${{ needs.build.outputs.coq_image_name }}