[TensorPipe Agent] Documentation fixes and nits (#39467)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/39467
Mainly cleaned up some docs and spelling/grammar nits
ghstack-source-id: 105457210
Test Plan: Sandcastle/CI
Differential Revision: D21755354
fbshipit-source-id: 28e7b925ace7813548a1bf8cdcf96cd423a227aa
