Update gradle.yml

Author: tonihele

.github/workflows/gradle.yml

@@ -36,7 +36,7 @@ jobs:
 
     steps:
     - name: Checkout the nightly-trigger repository
-      uses: actions/checkout@v2
+      uses: actions/checkout@v3
       with:
         repository: 'jMonkeyEngine/sdk-update-center'
         ref: nightly