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](actions/cache@v2.1.5...v2.1.6)

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

.github/workflows/ci.yml

@@ -25,7 +25,7 @@ jobs:
         java-version: '11'
         check-latest: true
     - name: Cache local Maven repository
-      uses: actions/cache@v2.1.5
+      uses: actions/cache@v2.1.6
       with:
         path: ~/.m2/repository
         key: ${{ runner.os }}-maven-${{ hashFiles('**/pom.xml') }}