fix the document of kaiming initialization (#25638)
Summary:
Based on https://github.com/pytorch/pytorch/issues/25549, I modified the comments for kaiming initialization in torch.nn.init.py
Pull Request resolved: https://github.com/pytorch/pytorch/pull/25638
Differential Revision: D17915392
Pulled By: vincentqb
fbshipit-source-id: 40f60c65d14790696ec03d7d91c764875efd6cf1
