Update GH actions workflow

.github/workflows/gradle.yml

@@ -1,17 +1,16 @@
-# This workflow will build a Java project with Gradle
-# For more information see: https://help.github.com/actions/language-and-framework-guides/building-and-testing-java-with-gradle
-
 name: Java CI with Gradle
 
 on: [push, pull_request]
 
 jobs:
   build:
+    if: ${{ github.event_name != 'pull_request' || github.repository != github.event.pull_request.head.repo.full_name }}
 
     runs-on: ubuntu-22.04
 
     steps:
     - uses: actions/checkout@v3
+    - uses: gradle/wrapper-validation-action@v1
     - name: Set up JDK 11
       uses: actions/setup-java@v3
       with: