[FX] Update overview docstring (#50896)
Summary: Pull Request resolved: https://github.com/pytorch/pytorch/pull/50896
Test Plan: Imported from OSS
Reviewed By: ansley
Differential Revision: D26002067
Pulled By: jamesr66a
fbshipit-source-id: 3b4d4b96017d16739a31f25a306f55b6f96324dc
