Add "API" to all API docs
What does this MR do?
Add "API" to all API docs
Follows CE-version https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/11450 and https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/11261
Related: https://gitlab.com/gitlab-org/gitlab-ce/issues/32307
cc/ @axil @SeanPackham