Typo in pytorch_vision_resnet.md

[JiaminShi]

https://github.com/pytorch/hub/blob/master/pytorch_vision_resnet.md#model-description "Here we have the 5 versions of resnet models, which contains 5, 34, 50, 101, 152 layers respectively". I believe it should be "Here we have the 5 versions of resnet models, which contains 18, 34, 50, 101, 152 layers respectively"

[nicklashansen]

Yes, this should get changed. Definitely a typo.