Bump actions/cache from 2.1.6 to 2.1.7 (#22)

Bumps [actions/cache](https://github.com/actions/cache) from 2.1.6 to 2.1.7.
- [Release notes](https://github.com/actions/cache/releases)
- [Commits](https://github.com/actions/cache/compare/v2.1.6...v2.1.7)

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

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

Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

.github/workflows/cache.yml

@@ -38,7 +38,7 @@ jobs:
       - name: Cache runners svn-2-git-fhem mirror directory  
         # Some room for improvement because we create a new cache on every run where a new ref is fetched, this isn't very nice, normaly we need only the last one and it takes 7 days until they are deleted
         id: cache-fhem
-        uses: actions/cache@v2.1.6
+        uses: actions/cache@v2.1.7
         with:
           path: |
             ./src/fhem-mirror/.git