proofreading (#29797)
Summary:
two instances of if -> it in torch.nn.modules.batchnorm.py
Pull Request resolved: https://github.com/pytorch/pytorch/pull/29797
Differential Revision: D19698613
Pulled By: ezyang
fbshipit-source-id: 7312b2333f227113e904dfa91db90d00e525affb
