Adds note about multi-deployment apps

doc/user/project/deploy_boards.md

@@ -41,6 +41,10 @@ knowledge. In particular, you should be familiar with:
 - [Kubernetes namespaces](https://kubernetes.io/docs/concepts/overview/working-with-objects/namespaces/)
 - [Kubernetes canary deployments](https://kubernetes.io/docs/concepts/cluster-administration/manage-deployment/#canary-deployments)
 
+NOTE: **Note:**
+Apps that consist of multiple deployments are shown as duplicates on the deploy board.
+Follow [this issue](https://gitlab.com/gitlab-org/gitlab/-/issues/8463) for details.
+
 ## Use cases
 
 Since the Deploy Board is a visual representation of the Kubernetes pods for a