Avoid variable shadowing in ``::at::philox_engine::single_round()`` (#27486)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/27486
Rename `key` argument of `single_round` method to `in_key`
Test Plan: CI
Reviewed By: stepancheg, soumith
Differential Revision: D17782904
fbshipit-source-id: 6feae55c407f39d41db099b013dcbd3990768603
