That'll resolve the violation for future releases. However, all previous releases are still infringing.
For a violating company who really doesn't want to open source their project, their best bet would probably be to (remove the dependency and) pay damages for previous infringement.
You'd hope damages in a case like this would be small given it went unnoticed for so long. Considering the shared-mime-info project itself is not commercial software, there probably wasn't significant damage to the project or the authors.
This is probably a first time I've seen damages mentioned in relation to GPL violations. Did anyone try enforce this?
[0]:https://wiki.fsfe.org/Migrated/GPL%20Enforcement%20Cases#Bus...
However, most non egrigious copyright infringement cases are more about stopping future infringement than damages. So I'd be surprised to see much GPL enforcement with damages.
IANAL, but I'm pretty sure this is _not_ how it works. Your code doesn't magically "become" licensed under GPL if you use GPL code. Your code is now in _violation_ of the GPL and one way of fixing it is to re-license your code. Another way is to eliminate the dependency.
However, if you decide to re-license to GPL then you may still have to pay damages for the time you were violating GPL.
In practice I can't imagine that a court would make anyone pay anything for this incident.