bring quantized_backward.cpp in sync with intern (#101990)
The version of [D45965552](https://www.internalfb.com/diff/D45965552) exported as #101739 was not the latest. This PR brings GH in sync with intern.
For Meta employees, see:
[D46056765](https://www.internalfb.com/diff/D46056765)
[D45965552](https://www.internalfb.com/diff/D45965552)
@diff-train-skip-merge
Pull Request resolved: https://github.com/pytorch/pytorch/pull/101990
Approved by: https://github.com/kit1980
