Upgrade to gradle/actions 6.1.0

(Clarified/updated licence is acceptable)

Author: mrotteveel

.github/workflows/run-tests.yml

@@ -49,8 +49,7 @@ jobs:
           java-version: ${{ matrix.java.javaInstall }}
           distribution: 'temurin'
       - name: Setup Gradle
-        # TODO: Review implications of license change before upgrading to version 6 or higher
-        uses: gradle/actions/setup-gradle@0723195856401067f7a2779048b490ace7a47d7c
+        uses: gradle/actions/setup-gradle@50e97c2cd7a37755bbfafc9c5b7cafaece252f6e
         with:
           cache-read-only: ${{ github.ref != 'refs/heads/master' }}
       - name: Build with Gradle