Pulp sync is broken on RL8

[sjpb]

At https://github.com/stackhpc/ansible-slurm-appliance/blob/main/ansible/adhoc/sync-pulp.yml#L10, because vars "win" over inventory, pulp_site_target_distribution_version can't be overridden to e.g. RL8.

[sjpb]

Probably the proper fix for this is to get rid of the adhoc entirely. Running either site or fatimage should be enough to sync Pulp, if enabled.