Don't build binaries on push

.github/workflows/build-python-package.yml

@@ -1,6 +1,10 @@
 name: Build & Publish Python Package
 
-on: [push, pull_request]
+# Trigger the workflow on push or pull request, but only for the master branch
+on:
+  pull_request:
+  push:
+    branches: [master]
 
 jobs:
   build_wheels: