[to #348] fix gh-pages can not deploy rendered documents (#409)

.github/workflows/gh-pages.yml

@@ -3,8 +3,7 @@ name: GitHub Pages
 on:
   push:
     branches:
-      - main
-  pull_request:
+      - master
 
 jobs:
   deploy:
@@ -24,7 +23,7 @@ jobs:
 
       - name: Deploy
         uses: peaceiris/actions-gh-pages@v3
-        if: ${{ github.ref == 'refs/heads/main' }}
+        if: ${{ github.ref == 'refs/heads/master' }}
         with:
           github_token: ${{ secrets.GITHUB_TOKEN }}
           publish_dir: ./docs/book