Change event_name for "Push PR preview".

Author: samsrabin

.github/workflows/docs.yml

@@ -89,7 +89,7 @@ jobs:
           make BUILDDIR=${PWD}/_build -C doc/ html
       - name: Push PR preview
         if: |
-          github.event_name == 'pull_request'
+          github.event_name == 'push'
         uses: peaceiris/actions-gh-pages@v3
         with:
           github_token: ${{secrets.GITHUB_TOKEN}}