[FX] Fix default to align with documentation in `fuser.py` (#53457)
Summary:
Currently it says it does a deepcopy by default, but that's not true.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/53457
Reviewed By: navahgar
Differential Revision: D26876781
Pulled By: Chillee
fbshipit-source-id: 26bcf76a0c7052d3577f217e79545480c9118a4e
