[numpy] polygamma: int -> float promotion (#57462)
Summary:
Reference: https://github.com/pytorch/pytorch/issues/42515
Pull Request resolved: https://github.com/pytorch/pytorch/pull/57462
Reviewed By: mrshenli
Differential Revision: D28187104
Pulled By: ezyang
fbshipit-source-id: 4072589ad1cb9766e7721d006d43701820922d56
