Fix push event to be triggered only on master

See: https://help.github.com/en/actions/automating-your-workflow-with-github-actions/events-that-trigger-workflows#example-using-multiple-events-with-activity-types-or-configuration

.github/workflows/test.yml

@@ -1,6 +1,8 @@
 name: Test
 on:
   push:
+    branches:
+      - master
   pull_request:
     types: [opened, reopened]
 jobs: