Merge branch 'docs/roadmap-missing-link' into 'master'

Add missing link to products for roadmaps docs

See merge request gitlab-org/gitlab-ee!4665

doc/user/group/roadmap/index.md

@@ -24,3 +24,5 @@ and finish date. If an epic doesn't have a planned finish date, the timeline bar
 away towards the future. Similarly, if an epic doesn't have a planned start date, the
 timeline bar becomes more visible as it approaches the epic's planned finish date on the
 timeline.
+
+[ee]: https://about.gitlab.com/products