quant docs: clean up hardswish (#40323)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/40323
Cleans up the naming and the function param docs for quantized hardswish.
Remove redundant docstrings and link to floating point modules instead.
Test Plan:
* build the docs on Mac OS
* verify that every link works as expected
Differential Revision: D22152638
Pulled By: vkuzo
fbshipit-source-id: fef04874ae460b449c677424a6a1c6dd47054795
