update Group Management

[erwangranger]

thanks to @MelissaFlinn for pointing out that this section could use a facelift:

https://ai-on-openshift.io/odh-rhoai/openshift-group-management/

among other things:

1. the hyperlink to the doc is stale and should point to https://docs.redhat.com/en/documentation/red_hat_openshift_ai_self-managed/2-latest/html/managing_openshift_ai/managing-users-and-groups#overview-of-user-types-and-permissions_managing-rhoai instead
2. lots of use of "rhods" would be better served by using "rhoai" instead.
3. probably a few more things.