Merge branch 'docs/ssot_admin_area_usage_statistics' into 'master'

Edit Admin Area's "Usage Statistics" for SSOT

See merge request gitlab-org/gitlab-ce!29110

doc/user/admin_area/settings/usage_statistics.md

+---
+type: reference
+---
+
 # Usage statistics
 
 GitLab Inc. will periodically collect information about your instance in order
@@ -83,6 +87,18 @@ of your instance to your users.
 This can be restricted to admins by selecting "Only admins" in the Instance
 Statistics visibility section under **Admin area > Settings > Usage statistics**.
 
+<!-- ## Troubleshooting
+
+Include any troubleshooting steps that you can foresee. If you know beforehand what issues
+one might have when setting this up, or when something is changed, or on upgrading, it's
+important to describe those, too. Think of things that may go wrong and include them here.
+This is important to minimize requests for support, and to avoid doc comments with
+questions that you know someone might ask.
+
+Each scenario can be a third-level heading, e.g. `### Getting error message X`.
+If you have none to add when creating a doc, leave this section in place
+but commented out to help encourage others to add to it in the future. -->
+
 [ee-557]: https://gitlab.com/gitlab-org/gitlab-ee/merge_requests/557
 [ee-735]: https://gitlab.com/gitlab-org/gitlab-ee/merge_requests/735
 [ce-23361]: https://gitlab.com/gitlab-org/gitlab-ce/issues/23361