ci: add Gradle `configuration-cache` encryption key

.github/workflows/android.yml

@@ -40,6 +40,8 @@ jobs:
 
     - name: Setup Gradle
       uses: gradle/actions/setup-gradle@v4
+      with:
+        cache-encryption-key: ${{ secrets.GRADLE_ENCRYPTION_KEY }}
 
     - name: Check lint
       run: ./gradlew lintFdroidDebug lintGoogleDebug