typo in code

[yu-yuxuan]

In tutorials/beginner_source/blitz/neural_networks_tutorial.py
The figure of the network that classifies digit images shows 16@5x5 in S4
So it should be self.fc1 = nn.Linear(16 * 5 * 5, 120) in line 15.

[holly1238]

Kernel size is 5x5. This was fixed in the tutorial in #1257.