build(ci): set keep_files to false

This will ensure that  the files in gh-pages branch will be deleted before copying the new files.

.github/workflows/ci.yaml

@@ -81,6 +81,7 @@ jobs:
         uses: peaceiris/actions-gh-pages@v3
         with:
           # this will use ladybugbot token
-          personal_token: ${{ secrets.GH_TOKEN }}
+          github_token: ${{ secrets.GITHUB_TOKEN }}
           publish_branch: gh-pages
           publish_dir: docs/_build/
+          keep_files: false