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)

Signed-off-by: dependabot[bot] <support@github.com>
diff --git a/.github/workflows/maven.yml b/.github/workflows/maven.yml
index 41bb31d..f28b6d9 100644
--- a/.github/workflows/maven.yml
+++ b/.github/workflows/maven.yml
@@ -36,7 +36,7 @@
         uses: actions/checkout@v2.3.4
 
       - name: Set up cache for ~./m2/repository
-        uses: actions/cache@v2.1.5
+        uses: actions/cache@v2.1.6
         with:
           path: ~/.m2/repository
           key: maven-${{ matrix.os }}-java${{ matrix.java }}-${{ hashFiles('**/pom.xml') }}