update profiler doc strings (#51395)
Summary:
Fixes formatting for autograd.profiler doc string (was broken), slightly expands profiler.profile documentation.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/51395
Reviewed By: ilia-cher
Differential Revision: D26162349
Pulled By: ngimel
fbshipit-source-id: ac7af8e0f3dbae2aa899ad815d2311c2758ee57c
