Move User Cohorts documentation to admin area

The User Cohorts feature has been moved to the Admin Area and is no
longer being considered an analytics feature. This moves documentation
about it from the Analytics documentation to the Admin Area
documentation

app/views/admin/users/_cohorts_table.html.haml

@@ -2,7 +2,7 @@
 .bs-callout.clearfix
   %p
     = s_("Cohorts|User cohorts are shown for the last %{months_included} months. Only users with activity are counted in the 'New users' column; inactive users are counted separately.") % { months_included: @cohorts[:months_included] }
-    = link_to sprite_icon('question-o'), help_page_path('user/admin_area/analytics/user_cohorts', anchor: 'cohorts'), title: 'About this feature', target: '_blank'
+    = link_to sprite_icon('question-o'), help_page_path('user/admin_area/user_cohorts', anchor: 'cohorts'), title: 'About this feature', target: '_blank'
 
 .table-holder.d-xl-table
   %table.table

doc/administration/index.md

@@ -130,7 +130,7 @@ Learn how to install, configure, update, and maintain your GitLab instance.
   - [Kerberos authentication](../integration/kerberos.md).
   - See also other [authentication](../topics/authentication/index.md#gitlab-administrators) topics (for example, enforcing 2FA).
 - [Email users](../tools/email.md): Email GitLab users from within GitLab.
-- [User Cohorts](../user/admin_area/analytics/user_cohorts.md): Display the monthly cohorts of new users and their activities over time.
+- [User Cohorts](../user/admin_area/user_cohorts.md): Display the monthly cohorts of new users and their activities over time.
 - [Audit events](audit_events.md): View the changes made within the GitLab server for:
   - Groups and projects.
   - Instances.

doc/user/admin_area/analytics/index.md

@@ -14,4 +14,3 @@ There are several kinds of statistics:
 
 - [DevOps Report](dev_ops_report.md): Provides an overview of your entire instance's feature usage. **(FREE)**
 - [Usage Trends](usage_trends.md): Shows how much data your instance contains, and how that is changing. **(FREE)**
-- [User Cohorts](user_cohorts.md): Display the monthly cohorts of new users and their activities over time. **(FREE)**

doc/user/admin_area/analytics/user_cohorts.md

 ---
-stage: none
-group: unassigned
-info: To determine the technical writer assigned to the Stage/Group associated with this page, see https://about.gitlab.com/handbook/engineering/ux/technical-writing/#assignments
+redirect_to: '../user_cohorts.md'
 ---
 
-# Cohorts **(FREE)**
+This document was moved to [another location](../user_cohorts.md).
 
-As a benefit of having the [usage ping active](../settings/usage_statistics.md),
-you can analyze your users' GitLab activities over time.
-
-To see user cohorts, go to **Admin Area > Overview > Users**.
-
-## Overview
-
-How do you interpret the user cohorts table? Let's review an example with the
-following user cohorts:
-
-![User cohort example](img/cohorts_v13_9.png)
-
-For the cohort of March 2020, three users were added to this server and have
-been active since this month. One month later (April 2020), two users are still
-active. Five months later (August 2020), one user from this cohort is still
-active, or 33% of the original cohort of three that joined in March.
-
-The **Inactive users** column shows the number of users who were added during
-the month, but who never had any activity in the instance.
-
-How do we measure the activity of users? GitLab considers a user active if:
-
-- The user signs in.
-- The user has Git activity (whether push or pull).
-- The user visits pages related to dashboards, projects, issues, or merge
-  requests ([introduced](https://gitlab.com/gitlab-org/gitlab-foss/-/issues/54947) in GitLab 11.8).
-- The user uses the API.
-- The user uses the GraphQL API.
+<!-- This redirect file can be deleted after <2021-06-01>. -->
+<!-- Before deletion, see: https://docs.gitlab.com/ee/development/documentation/#move-or-rename-a-page -->

doc/user/admin_area/index.md

@@ -186,6 +186,10 @@ The following totals are also included:
 
 GitLab billing is based on the number of [**Billable users**](../../subscriptions/self_managed/index.md#billable-users).
 
+### User cohorts
+
+The [Cohorts](user_cohorts.md) tab displays the monthly cohorts of new users and their activities over time.
+
 ### Administering Groups
 
 You can administer all groups in the GitLab instance from the Admin Area's Groups page.

doc/user/admin_area/user_cohorts.md

+---
+stage: none
+group: unassigned
+info: To determine the technical writer assigned to the Stage/Group associated with this page, see https://about.gitlab.com/handbook/engineering/ux/technical-writing/#assignments
+---
+
+# Cohorts **(FREE)**
+
+As a benefit of having the [usage ping active](settings/usage_statistics.md),
+you can analyze your users' GitLab activities over time.
+
+To see user cohorts, go to **Admin Area > Overview > Users**.
+
+## Overview
+
+How do you interpret the user cohorts table? Let's review an example with the
+following user cohorts:
+
+![User cohort example](img/cohorts_v13_9.png)
+
+For the cohort of March 2020, three users were added to this server and have
+been active since this month. One month later (April 2020), two users are still
+active. Five months later (August 2020), one user from this cohort is still
+active, or 33% of the original cohort of three that joined in March.
+
+The **Inactive users** column shows the number of users who were added during
+the month, but who never had any activity in the instance.
+
+How do we measure the activity of users? GitLab considers a user active if:
+
+- The user signs in.
+- The user has Git activity (whether push or pull).
+- The user visits pages related to dashboards, projects, issues, or merge
+  requests ([introduced](https://gitlab.com/gitlab-org/gitlab-foss/-/issues/54947) in GitLab 11.8).
+- The user uses the API.
+- The user uses the GraphQL API.