Bump actions/cache from 2.1.4 to 2.1.6

Bumps [actions/cache](https://github.com/actions/cache) from 2.1.4 to 2.1.6.
- [Release notes](https://github.com/actions/cache/releases)
- [Commits](actions/cache@v2.1.4...v2.1.6)

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

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

Author: dependabot[bot]

.github/workflows/maven.yml

@@ -27,7 +27,7 @@ jobs:
     # Nevertheless the repositories should be more stable and it makes no sense to pull
     # a same version every time
     # A dry run would make more sense
-    - uses: actions/cache@v2.1.4
+    - uses: actions/cache@v2.1.6
       with:
         path: ~/.m2/repository
         key: ${{ runner.os }}-maven-${{ hashFiles('**/pom.xml') }}