Merge branch 'docs/ssot_insights' into 'master'

Edit "Insights" content to meet SSOT guidelines

See merge request gitlab-org/gitlab-ce!29238

doc/user/group/insights/index.md

+---
+type: reference, howto
+---
+
 # Insights **[ULTIMATE]**
 
 > Introduced in [GitLab Ultimate](https://about.gitlab.com/pricing/) 11.9 behind the `insights` feature flag.
@@ -44,3 +48,15 @@ access to the project they belong to, or because they are confidential) are
 filtered out of the Insights charts.
 
 You may also consult the [group permissions table](../../permissions.md#group-members-permissions).
+
+<!-- ## 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. -->