Fix branch name in Github action

Author: kwkwan

.github/workflows/build_deploy.yml

@@ -53,7 +53,7 @@ jobs:
     environment:
       name: github-pages
       url: ${{ steps.deployment.outputs.page_url }}
-    if: ${{ github.ref == 'refs/heads/main' }}
+    if: ${{ github.ref == 'refs/heads/master' }}
     runs-on: ubuntu-latest
     needs: build
     steps: