Replace getargspec with getfullargspec (#15396)
Summary:
Replace `getargspec` with `getfullargspec` to resolve test warnings. Fixes #15344 .
Pull Request resolved: https://github.com/pytorch/pytorch/pull/15396
Differential Revision: D13529548
Pulled By: zou3519
fbshipit-source-id: 50d3be92423a9ce89bc4895b67569663e1abbaa6
