Hide the info mentioning the linked LDAP groups if you are not logged in.

As mentioned by a customer here: https://gitlab.zendesk.com/agent/tickets/15466

When a group contains public projects, it is possible to get at it's members without being logged in, but this page also leaks information if it is synched with LDAP. The DN of the linked groups will be shown:

This MR fixes that in that it only shows that information if the user is logged in.

/cc @DouweM