add explanation of quantized comparison strategy in assert_close (#68911)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/68911
Closes #68548.
Test Plan: Imported from OSS
Reviewed By: ngimel
Differential Revision: D33542997
Pulled By: mruberry
fbshipit-source-id: 78accf20a83cd72254ae0036dc23f9e5376a4c65
