Use GITHUB_TOKEN secret.

Author: gkellogg

.github/workflows/generate-docs.yml

@@ -22,6 +22,6 @@ jobs:
       - name: Deploy
         uses: peaceiris/actions-gh-pages@v3
         with:
-          github_token: $
+          github_token: ${{ secrets.GITHUB_TOKEN }}
           publish_dir: ./doc/yard
           publish_branch: gh-pages