Copyedit Epics docs
What does this MR do?
Follows up some remarks from the epic docs MR https://gitlab.com/gitlab-org/gitlab-ee/merge_requests/3393 that documents the new Epics feature https://gitlab.com/gitlab-org/gitlab-ee/issues/3254.
Closes https://gitlab.com/gitlab-org/gitlab-ee/issues/4062
Review http://ee-docs-copyedit-epics.178.62.207.141.xip.io/ee/user/group/index.html#epics
Edited by 🤖 GitLab Bot 🤖