Update link of ImageNet preprocessing

It was pointing to an old version where the validation pre-processing was the same as the training pre-processing, and thus had randomness in it (instead of CenterCrop).

Author: fmassa

docs/source/datasets.rst

@@ -87,7 +87,7 @@ The data is preprocessed `as described
 here <https://github.com/facebook/fb.resnet.torch/blob/master/INSTALL.md#download-the-imagenet-dataset>`__
 
 `Here is an
-example <https://github.com/pytorch/examples/blob/27e2a46c1d1505324032b1d94fc6ce24d5b67e97/imagenet/main.py#L48-L62>`__.
+example <https://github.com/pytorch/examples/blob/e0d33a69bec3eb4096c265451dbb85975eb961ea/imagenet/main.py#L113-L126>`__.
 
 CIFAR
 ~~~~~