ci: update to latest actions-gh-pages@v4

Author: jpgrayson

.github/workflows/publish.yml

@@ -28,7 +28,7 @@ jobs:
         run: hugo
 
       - name: Deploy to master
-        uses: peaceiris/actions-gh-pages@v3
+        uses: peaceiris/actions-gh-pages@v4
         with:
           github_token: ${{ secrets.GITHUB_TOKEN }}
           publish_dir: ./public