[ONNX] Support exporting with Apex O2 (#65374) (#66700)
Summary:
Apex O2 hook state_dict to return fp16 weights as fp32. Exporter cannot identify them as same tensors.
Since this hook is only used by optimizer, it is safe to remove this hook while exporting.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/66700
Reviewed By: zou3519
Differential Revision: D31695132
Pulled By: malfet
fbshipit-source-id: 977bdf57240002498f3ad0f1a8046c352e9860e6
