Fix CI running all actions twice on PR

this style of CI makes it that CI only runs on PRs and push to master branch instead of all PRs and all pushes (include push to PR which makes the  CI run twice each time)

.github/workflows/ci.yml

@@ -1,5 +1,8 @@
 name: CI
-on: [push, pull_request]
+on:
+  pull_request:
+  push:
+    branches: [ master ]
 
 jobs:
   build-linux-gcc: