[rpc][easy] remove code duplication on ProcessGroupAgent::enqueueSend (#35311)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/35311
This must have snuck in since a couple PRs updated this same area and
the merge conflict was not resolved properly.
ghstack-source-id: 100770387
Test Plan: CI
Differential Revision: D20602683
fbshipit-source-id: 22134069194b4095dd3be920e4e7f4437dac06f0
