Add a link in the docs to the epic that defined the Insights feature

Signed-off-by: Rémy Coutable <remy@rymai.me>

doc/user/group/index.md

@@ -218,6 +218,8 @@ Get an overview of the vulnerabilities of all the projects in a group and its su
 
 ## Insights **[ULTIMATE]**
 
+> [Introduced](https://gitlab.com/groups/gitlab-org/-/epics/725) in [GitLab Ultimate](https://about.gitlab.com/pricing/) 12.0.
+
 Configure the Insights that matter for your groups or projects, allowing users
 to explore data such as:
 

doc/user/group/insights/index.md

@@ -4,8 +4,7 @@ type: reference, howto
 
 # Insights **[ULTIMATE]**
 
-> Introduced in [GitLab Ultimate](https://about.gitlab.com/pricing/) 11.9 behind the `insights` feature flag.
-> **Generally Available** (GA) in [GitLab Ultimate](https://about.gitlab.com/pricing/) 12.0.
+> [Introduced](https://gitlab.com/groups/gitlab-org/-/epics/725) in [GitLab Ultimate](https://about.gitlab.com/pricing/) 12.0.
 
 Configure the Insights that matter for your groups to explore data such as
 triage hygiene, issues created/closed per a given period, average time for merge

doc/user/project/insights/index.md

 # Insights **[ULTIMATE]**
 
-> Introduced in [GitLab Ultimate](https://about.gitlab.com/pricing/) 11.9 behind the `insights` feature flag.
-> **Generally Available** (GA) in [GitLab Ultimate](https://about.gitlab.com/pricing/) 12.0.
+> [Introduced](https://gitlab.com/groups/gitlab-org/-/epics/725) in [GitLab Ultimate](https://about.gitlab.com/pricing/) 12.0.
 
 Configure the Insights that matter for your projects to explore data such as
 triage hygiene, issues created/closed per a given period, average time for merge