Bump actions/cache from 2.1.5 to 2.1.6

diff --git a/.github/workflows/maven.yml b/.github/workflows/maven.yml
index cf00a6b..9eaa3a5 100644
--- a/.github/workflows/maven.yml
+++ b/.github/workflows/maven.yml
@@ -33,7 +33,7 @@
         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-${{ matrix.os }}-${{ hashFiles('**/pom.xml') }}