gradle.yml: checkout the repo when not PR trigger (#35558)

Author: alafanechere

.github/workflows/gradle.yml

@@ -27,6 +27,9 @@ jobs:
       python_cdk: ${{ steps.changes.outputs.python_cdk }}
 
     steps:
+      - name: Checkout Airbyte
+        if: github.event_name != 'pull_request'
+        uses: actions/checkout@v3
       - id: changes
         uses: dorny/paths-filter@v2
         with: