Bump actions/cache from 1 to 4 (#23)

Bumps [actions/cache](https://github.com/actions/cache) from 1 to 4.
- [Release notes](https://github.com/actions/cache/releases)
- [Changelog](https://github.com/actions/cache/blob/main/RELEASES.md)
- [Commits](actions/cache@v1...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>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

.github/workflows/ci.yml

@@ -18,7 +18,7 @@ jobs:
     steps:
       - uses: actions/checkout@v2
 
-      - uses: actions/cache@v1
+      - uses: actions/cache@v4
         with:
           path: ${{ env.BUILD_CACHE }}
           key: ${{ hashFiles('Dockerfile') }}