driveby to only run the ghp deploy on main

.github/workflows/publish_github_pages.yml

@@ -30,6 +30,7 @@ jobs:
   deploy:
     runs-on: ubuntu-latest
     needs: build
+    if: github.ref == 'refs/heads/main'
     environment:
       name: github-pages
       url: ${{ steps.deploy.outputs.page_url }}