ci: remove push trigger from CI workflow

- remove push trigger for main and dev branches
- keep pull request trigger for main branch

Author: johelder

.github/workflows/ci.yml

@@ -1,9 +1,5 @@
 name: CI
 on:
-  push:
-    branches:
-      - main
-      - dev
   pull_request:
     branches:
       - main