[PyTorch][Static Runtime][easy] Fix ValueGroup comment (#66965)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/66965
external aliases aren't defined to be outputs (though output aliases may end up in there as the following sentence clarifies).
ghstack-source-id: 141473794
Test Plan: review
Reviewed By: mikeiovine
Differential Revision: D31809715
fbshipit-source-id: 82d1391b04e22559932f82270669a7ff94a1c90f
