[FX] Gate FXGraphDrawer on whether pydot is installed (#65088)
Summary: Pull Request resolved: https://github.com/pytorch/pytorch/pull/65088
Test Plan: Imported from OSS
Reviewed By: khabinov
Differential Revision: D30967951
Pulled By: jamesr66a
fbshipit-source-id: dba2f13a47889b3d4187de925b4fe74ee90b7f79
