Add group name badge under group milestone

What does this MR do?

Adds Group name badge under milestone within Milestones dashboard which was missed out from https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/20618.

Screenshots

Before	After

Does this MR meet the acceptance criteria?

• Changelog entry added, if necessary
• [ ] Documentation created/updated
• Tests added for this feature/bug
• Conforms to the code review guidelines
• Conforms to the merge request performance guidelines
• Conforms to the style guides
• [ ] Conforms to the database guides

Closes #49292 (closed)