Merge queue does not remove closed requests

Under certain circumstances, works are not cleared out of the merge queue despite having been merged. This seems usually to happen if a librarian set a primary work in the URL and that is later ignored by the librarian doing the merge.

### Evidence / Screenshot (if possible)


### Relevant url?

https://openlibrary.org/merges

### Steps to Reproduce

1. Go to Merge list
2. Click on "merge" to review a merge request
3. Remove a primary work set by a librarian from the URL
4. Either merge or reject the merge
5. The merge request remains in the list, even though it has been dealt with.

* Actual: Merge request remains in review limbo.
* Expected: Merge request is closed.

### Details

- **Logged in (Y/N)?**
- Y
- **Browser type/version?**
- Firefox 107 (64 bit)
- **Operating system?**
- Suse Tumbleweed
- **Environment (prod/dev/local)?** prod
- prod

### Proposal & Constraints

I have no idea how that could be solved. At the moment, I manually re-open the request and then close it.

### Related files

#6996
#6816

### Stakeholders

Librarians with merge capabilities
@seabelis @mheiman @mekarpeles