[PyTorch Edge] Update iOS readme to use lite interpreter (#59841)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/59841
As lite interpreter moves to beta, it's recommended to let users start using it.
ghstack-source-id: 131766778
Test Plan: CI
Reviewed By: husthyc
Differential Revision: D29048350
fbshipit-source-id: 54d2ad09b4e9475304522c80b358647bcea79b14
