fix check-label step

.github/workflows/pr_ok_to_test.yaml

@@ -21,10 +21,11 @@ jobs:
   build_minikube:
     runs-on: ubuntu-18.04
     steps:
-      - uses: NathanielHill/check-pr-label-action@v4.0.0
+      - name: Check ok-to-test label
+        uses: shioyang/check-pr-labels-on-push-action@v1.0.3
         with:
           github-token: '${{ secrets.GITHUB_TOKEN }}'
-          valid-labels: 'ok-to-test'
+          valid-labels: '["ok-to-test"]'
 
       - uses: actions/checkout@v2
       - uses: actions/setup-go@v2