[RPC] delete torch/csrc/utils/future.h (#51698)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/51698
Completely eliminates torch::utils::Future as we are now full relying on JitFuture.
ghstack-source-id: 122037612
Test Plan: CI
Reviewed By: kiukchung
Differential Revision: D26243735
fbshipit-source-id: 95010a730f9d35e618f74c5f9de482738cd57c15
