anyway we don't need authorization here.
Also retry does not seem to work in the original version, so let's
extend this with retries as a separate github action later.
because it randomly fails on authorization like:
https://github.com/ruby/ruby/runs/190887455
Also the backoff seems too short. Maybe we need tool/travis_retry.sh for
this too.
Cloning ruby/ruby does not need authorization. We don't need to use
actions/checkout.