Fix gcloud tag

Author: ravwojdyla

.github/workflows/validation.yml

@@ -14,7 +14,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
     - uses: actions/checkout@v2
-    - uses: google-github-actions/setup-gcloud@master
+    - uses: google-github-actions/setup-gcloud@v0
       with:
         project_id: ${{ secrets.GCP_PROJECT_ID }}
         service_account_key: ${{ secrets.GCP_SA_KEY }}