ci: update GitHub Pages action

Author: mario-zelger

.github/workflows/deploy.yml

@@ -62,7 +62,7 @@ jobs:
           path: ./build
 
       - name: Deploy to GH Pages
-        uses: peaceiris/actions-gh-pages@v3
+        uses: peaceiris/actions-gh-pages@v4
         with:
           github_token: ${{ secrets.GITHUB_TOKEN }}
           publish_dir: ./build