Fix fx patch module name (#61062)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/61062
Instead of being 'patch' this should be the import-able name of the module (it's defined as `_fx` on the `torch._C` module, so the full name should be `torch._C._fx`). This now works correctly:
```python
>>> import torch._C._fx
>>> dir(torch._C._fx)
['__doc__', '__loader__', '__name__', '__package__', '__spec__', 'patch_function']
```
Test Plan: Imported from OSS
Reviewed By: Chillee
Differential Revision: D29497018
Pulled By: driazati
fbshipit-source-id: 093aa0552b48feb0aabe47bdf72776dddd5a3b8f
