Define the `conflicting_mr` variable at the controller level instead of in the HAML document
The following discussion from !180675 should be addressed:
- [ ] @patrickbajao started a [discussion](https://gitlab.com/gitlab-org/gitlab/-/merge_requests/180675#note_2407137458):
> I think this variable should be set at the controller level. But since these are copied from an existing view file, we can do this in a follow up issue/MR.
issue