Fixed wrong link of MNIST (#2760)

Signed-off-by: GitHub <noreply@github.com>
Co-authored-by: Nicolas Hug <contact@nicolas-hug.com>

Author: Aisuko

recipes_source/recipes/defining_a_neural_network.py

@@ -17,7 +17,7 @@
 
 In this recipe, we will use ``torch.nn`` to define a neural network
 intended for the `MNIST
-dataset <https://pytorch.org/docs/stable/torchvision/datasets.html#mnist>`__.
+dataset <hhttps://pytorch.org/vision/stable/generated/torchvision.datasets.MNIST.html#torchvision.datasets.MNIST>`__.
 
 Setup
 -----