Get rid of pluck in app/services/members/authorized_destroy_service.rb

https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/11417#note_29808649

mentioned in merge request !11417 (merged)

added ~480950 backstage labels

mentioned in merge request !11433 (merged)

closed via merge request !11433 (merged)

mentioned in commit f0caffe9