ci: get event name from correct place

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

.github/workflows/main.yml

@@ -82,7 +82,7 @@ jobs:
     runs-on: ubuntu-latest
     needs: test
     # Trigger release for only pushes to branches defined above
-    if: github.event == 'push'
+    if: github.event_name == 'push'
     steps:
       - uses: actions/checkout@v2
       - uses: actions/setup-node@v1