Cluster admin contact info needs clearer labeling

[cnweaver]

On the non-owner cluster pages (e.g. https://portal.slateci.io/clusters/uchicago-prod) at least one user has been confused that there is no way to edit the contact info. This is because this information is a property of the administering group, and must be edited there. It seems like it would be better to somehow indicate this on the page, either through layout or changing the label to be more specific.