Avoid re-doing CUDA stream sync in OwnerRRef (#57355)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/57355
We had started fixing OwnerRRef to make it CUDA-compatible, by properly synchronizing CUDA streams/events where appropriate. However, since we started using CUDAFuture (or, well, ivalue::Future nowadays, after they got merged) this is all done automatically for us, hence we can undo these "fixes" as they're now duplicated.
ghstack-source-id: 130583771
Test Plan: CI
Reviewed By: mrshenli
Differential Revision: D28118182
fbshipit-source-id: 4b1dd9fe88c23802b1df573941d1b73af48bb67b
