GitHub Actions: remove Gradle validation step

Author: hsz

.github/workflows/tests.yml

@@ -15,10 +15,6 @@ jobs:
       - name: Fetch Sources
         uses: actions/[email protected]
 
-      # Validate wrapper
-      - name: Gradle Wrapper Validation
-        uses: gradle/[email protected]
-
       # Setup Java 11 environment for the next steps
       - name: Setup Java
         uses: actions/setup-java@v2