Update peaceiris action version

Author: SilkeSchomann

.github/workflows/online_doc_update.yml

@@ -13,7 +13,7 @@ jobs:
       uses: sphinx-notes/pages@v3
       with:
         publish: false
-    - uses: peaceiris/actions-gh-pages@v3
+    - uses: peaceiris/actions-gh-pages@v4
       with:
         github_token: ${{ secrets.GITHUB_TOKEN }}
         publish_dir: ${{ steps.deployment.outputs.artifact }}