[DOC] - Improvements to Creating and managing groups doc

[kcpevey]

Preliminary Checks

• This issue is not a question, feature request, RFC, or anything other than a bug report. Please post those things in GitHub Discussions: https://github.com/nebari-dev/nebari/discussions

Summary

There are a couple of places in this doc like this:

Navigate to the Group: Log in to Keycloak as an administrator and select the group.
Go to Role Mappings: Click on the Role Mappings tab.

or

Navigate to the Group's Role Mappings: Select the group and go to the Role Mappings tab.

but its missing a step. After you select the group, there is no Role Mappings tab - you have to click Edit first.