Merge branch 'docs/ssot_epics' into 'master'

Edited "Epics" to comply with SSOT

See merge request gitlab-org/gitlab-ce!29236

doc/user/group/epics/index.md

+---
+type: reference, howto
+---
+
 # Epics **[ULTIMATE]**
 
 > Introduced in [GitLab Ultimate][ee] 10.2.
@@ -215,3 +219,15 @@ Once you wrote your comment, you can either:
 ## Notifications            
 
 - [Receive notifications](../../../workflow/notifications.md) for epic events.
+
+<!-- ## 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. -->