Update peaceiris/actions-gh-pages action to v4

| datasource  | package                    | from | to |
| ----------- | -------------------------- | ---- | -- |
| github-tags | peaceiris/actions-gh-pages | v3   | v4 |

Author: renovate[bot]

.github/workflows/githubpages.yaml

@@ -19,7 +19,7 @@ jobs:
           arguments: -Pversion=${{ github.event.release.tag_name }} dokkaHtml
 
       - 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: ./docs