fixup! Run label check workflow only on label events and open pr event

Author: kyu08

.github/workflows/check-required-label.yml

@@ -7,7 +7,6 @@ on:
 jobs:
   check-required-label:
     runs-on: ubuntu-latest
-    if: github.ref != 'refs/heads/master'
     steps:
       - uses: mheap/github-action-required-labels@v5
         with: