Revert "System user does not count in service desk license."

This reverts commit fa1ff54f

doc/user/project/service_desk.md

@@ -109,11 +109,6 @@ you can read and write comments as you normally do:
 
 > Note that the project's visibility (private, internal, public) does not affect Service Desk.
 
-### System user
-
-Behind the scenes, Service Desk works by a system user creating issues. This system user
-does not count toward the license limit count.
-
 [ee-149]: https://gitlab.com/gitlab-org/gitlab-ee/issues/149 "Service Desk with email"
 [ee]: https://about.gitlab.com/gitlab-ee/ "GitLab Enterprise Edition landing page"
 [eep-9.1]: https://about.gitlab.com/2017/04/22/gitlab-9-1-released/#service-desk-eep