Fix approve button showing closed merge requests
What does this MR do?
Approve/Approve Additionally button when a merge request is
Original "Approve additionally" MR, https://gitlab.com/gitlab-org/gitlab-ee/merge_requests/4033
Does this MR meet the acceptance criteria?
- Changelog entry added, if necessary
- Tests added for this feature/bug
- Has been reviewed by Frontend
- Conform by the merge request performance guides
- Conform by the style guides
- Squashed related commits together