Dashboard group milestones should only show from groups you are a member of
Currently, dashboard milestones include all public group milestones regardless if you are a member of that group.
Steps to reproduce
What is the current bug behavior?
The milestone list includes all public group milestones. This is also reproduced on GitLab.com.
What is the expected correct behavior?
The milestone list should include only group milestones of the groups that you are a member of.