[EE-Port] Allow to promote group milestones
CE merge request - https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/14831
This is necessary because EE have boards which can belong to milestones.
Edited by Coung Ngo
CE merge request - https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/14831
This is necessary because EE have boards which can belong to milestones.