Deploy only on push to main

Author: matt-graham

.github/workflows/docs.yml

@@ -45,7 +45,7 @@ jobs:
         cd docs && make html
 
     - name: Deploy
-      if: github.ref == 'refs/heads/main'
+      if: github.event_name == 'push' && github.ref == 'refs/heads/main'
       uses: JamesIves/github-pages-deploy-action@v4.7.3
       with:
         branch: gh-pages # The branch the action should deploy to.