[FX] Only copy over forward() from exec (#44006)
Summary: Pull Request resolved: https://github.com/pytorch/pytorch/pull/44006
Test Plan: Imported from OSS
Reviewed By: zdevito
Differential Revision: D23466542
Pulled By: jamesr66a
fbshipit-source-id: 12a1839ddc65333e3e3d511eeb53206f06546a87
