Avoid duplicated C.I. runs

.github/workflows/ci.yml

@@ -1,12 +1,7 @@
 name: ci
 run-name: ${{ github.actor }} is testing out GitHub Actions 🚀
 
-on:
-    push:
-    pull_request:
-        branches:
-            - main
-            - master
+on: [push]
 
 jobs:
   windows-latest: