Fix gradle/gradle-build-action@v2 warnings

Avoid:
```
Node.js 16 actions are deprecated.
Please update the following actions to use Node.js 20: gradle/gradle-build-action@v2.
For more information see: https://github.blog/changelog/2023-09-22-github-actions-transitioning-from-node-16-to-node-20/.
```

.github/workflows/ci.yml

@@ -23,11 +23,10 @@ jobs:
     steps:
     - name: Checkout
       uses: actions/checkout@v4
+    - name: Setup Gradle
+      uses: gradle/actions/setup-gradle@v3
     - name: Build
-      uses: gradle/gradle-build-action@v2
-      with:
-        gradle-version: wrapper
-        arguments: build
+      run: ./gradlew build
     - name: Upload diagnoses
       if: always()
       uses: actions/upload-artifact@v4