I'm just a fellow simmer in the UK, but I believe GPU caches store data that the system may wish to use quickly in future. The data stored in a cache might be the result of an earlier computation, or the duplicate of data stored elsewhere.
Unless you plan to do anything with the folder, I guess it could be deleted without concern as the system would no doubt rebuild another cache folder very quickly if required.
Maybe someone with knowledge of such things would be able to confirm?
Personally I don't have this folder currently in my X-Plane root directory?