* Don't print the empty list for the vast majority of realms where
this is a noop.
* Make output a little more clear that this isn't revoking all
Confirmations, just those associated with deactivated users.
This is a natural follow-up to
93e8740218 - invitations sent by users
deactivated before the commit still need to be revoked, via a
migration.
The logic for finding the Confirmations to deactivated is based on
get_valid_invite_confirmations_generated_by_user in actions.py.