Comment 1 for bug 1946090

This is due to the un-puppetisation of certmonger service: back in train, a "certmonger_user" service was created here:
https://opendev.org/openstack/tripleo-heat-templates/src/branch/stable/train/deployment/certs/certmonger-user-baremetal-puppet.yaml#L63

Now, it's has been removed, and so the hostgroup as well.

Thanks aschultz and slagle for the digging :)