CI: activate Github actions for pushes to backport branch (1.2.x)

[simonjayhawkins]

xref #39295 (comment)

for the Github actions issue, I should open a new issue and xref #38360. we may want to activate Github actions for pushes to 1.2.x and update .github\workflows\ci.yml which will currently upload docs on a push event...

    - name: Upload web
      run: rsync -az --delete --exclude='pandas-docs' --exclude='docs' --exclude='Pandas_Cheat_Sheet*' web/build/ docs@${{ secrets.server_ip }}:/usr/share/nginx/pandas
      if: github.event_name == 'push'