remove `randn?` from `torch.testing` namespace (#61840)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/61840
Redo of #60859.
Test Plan: Imported from OSS
Reviewed By: jbschlosser
Differential Revision: D29871017
Pulled By: mruberry
fbshipit-source-id: 47afed1dc6aa0bb1e826af616ef5d5aaabb8e5bb
