Fix "Migrations altering Appearances need to clear cache"
Clears the current_appearance
cache so we don't get errors such as https://sentry.gitlap.com/gitlab/staginggitlabcom/issues/158428/ after the migrations.
It also reverts https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/18211
A proper fix would be to implement what @rymai sketeched here: https://gitlab.com/gitlab-org/gitlab-ee/issues/5571#note_66985230
Closes https://gitlab.com/gitlab-org/gitlab-ee/issues/5571#note_66985230
Edited by James Lopez