Bump actions/cache from 2.1.5 to 2.1.6

Bumps [actions/cache](https://github.com/actions/cache) from 2.1.5 to 2.1.6.
- [Release notes](https://github.com/actions/cache/releases)
- [Commits](https://github.com/actions/cache/compare/v2.1.5...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>

.github/workflows/maven.yml

@@ -18,7 +18,7 @@ jobs:
         distribution: 'adopt'
 
     - name: Cache Maven packages
-      uses: actions/cache@v2.1.5
+      uses: actions/cache@v2.1.6
       with:
         path: ~/.m2
         key: ${{ runner.os }}-m2-${{ hashFiles('**/pom.xml') }}