Remove _uses_true_division (#35618)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/35618
Python 2 has reached end-of-life and is no longer supported by PyTorch.
Python 3 always uses true division.
Test Plan: CI
Differential Revision: D20842884
Pulled By: dreiss
fbshipit-source-id: 522e34bb584d4bdb01c9c40eb267955062a57774
