[Core ML] Fix error messages (#67410)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/67410
As title
ghstack-source-id: 141537215
Test Plan: buck-test pp-ios
Reviewed By: hanton
Differential Revision: D31901372
fbshipit-source-id: 80ae1cf8cb67c0e2ca276e21cc80b1ff799437a4
