Add a disclaimer about limited CUDA support in RPC (#58023)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/58023
Clearly state that some features of RPC aren't yet compatible with CUDA.
ghstack-source-id: 128688856
Test Plan: None
Reviewed By: agolynski
Differential Revision: D28347605
fbshipit-source-id: e8df9a4696c61a1a05f7d2147be84d41aeeb3b48
