[5.x] Avoid showing asset upload fixes when inappropriate

[jasonvarga]

Fixes #10980

I went with a 409 Conflict status as it seems the most appropriate:

The request could not be completed due to a conflict with the current state of the target resource. This code is used in situations where the user might be able to resolve the conflict and resubmit the request.

Now you will only get the option to "fix" the upload when its due to being a duplicate. Regular validation errors and file size limit issues will not.