test: Run conventional-commit-check only on PR's, not pushes. (#6688)

https://github.blog/changelog/2019-10-01-github-actions-new-workflow-syntax-features/#if-at-the-job-level

Author: joyzhong

.github/workflows/test.yml

@@ -18,6 +18,7 @@ jobs:
       - run: npm install
       - run: npm run lint
   conventional-commit-check:
+    if: github.event_name == 'pull_request'
     runs-on: ubuntu-latest
     steps:
       - uses: amannn/[email protected]