Fix group milestone path on issuable sidebar
What does this MR do?
Fix the milestone link in the issuable sidebar when an issue / MR has a group milestone assigned.
Are there points in the code the reviewer needs to double check?
milestone_url isn't strictly needed here, but I will need it later anyway, and it's nice to have for consistency.
Why was this MR needed?
It fixes a regression!
Does this MR meet the acceptance criteria?
- Changelog entry added, if necessary
- Added for this feature/bug
- All builds are passing
- Has been reviewed by Backend
- Conform by the merge request performance guides
- Conform by the style guides
Branch has no merge conflicts with
master(if it does - rebase it please)
- Squashed related commits together