Lock version of actions-gh-pages

Author: Cito

.github/workflows/release-docs.yml

@@ -26,7 +26,7 @@ jobs:
         make html
         touch _build/html/.nojekyll
     - name: Deploy docs to GitHub pages
-      uses: peaceiris/actions-gh-pages@v3
+      uses: peaceiris/actions-gh-pages@v3.5.10
       with:
         github_token: ${{ secrets.GITHUB_TOKEN }}
         publish_branch: gh-pages