Merge branch 'docs-group-instance-clusters-ga' into 'master'

Remove beta from group and instance clusters

See merge request gitlab-org/gitlab-ce!31059

doc/user/group/clusters/index.md

@@ -5,7 +5,6 @@ type: reference
 # Group-level Kubernetes clusters
 
 > [Introduced](https://gitlab.com/gitlab-org/gitlab-ce/issues/34758) in GitLab 11.6.
-> Group Cluster integration is currently in [Beta](https://about.gitlab.com/handbook/product/#alpha-beta-ga).
 
 ## Overview
 

doc/user/instance/clusters/index.md

 # Instance-level Kubernetes clusters
 
 > [Introduced](https://gitlab.com/gitlab-org/gitlab-ce/issues/39840) in GitLab 11.11.
-> Instance-level cluster integration is currently in [Beta](https://about.gitlab.com/handbook/product/#alpha-beta-ga).
 
 ## Overview