[rpc] Remove redundant call to createExceptionResponse (#36857)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/36857
This was a redundant call as we immediately took the msg and conerted
it back to a string
ghstack-source-id: 102424018
Test Plan: CI
Differential Revision: D21104235
fbshipit-source-id: 4124007d800dbe2718ddebb40281d0a86484685e
