Invitation user experience [PD-874]

Removes the activation link for active users. The ticket also specifies adding a link to manage PRM, but we decided against it in our meeting.
whoops, read 0, not 1. In any case, do activation links have a class? If so, can we check for that (not that we use any other links). Otherwise, can we note that explicitly that we're looking for activation links. It's obvious now, but I dont' know if I'm going to remember that outside the context of a PR specifically for invitation emails.