Typo (pytorch#139)

I have made some performance improvements to the model, and testing them now. If results turn out good, I will submit a separate PR.

Author: FuriouslyCurious

torchvision/models/densenet.py

@@ -55,7 +55,7 @@ def densenet201(pretrained=False, **kwargs):
 
 
 def densenet161(pretrained=False, **kwargs):
- r"""Densenet-201 model from
+ r"""Densenet-161 model from
  `"Densely Connected Convolutional Networks" <https://arxiv.org/pdf/1608.06993.pdf>`
 
  Args: