Fix typo in docstring example (pytorch#2562)

Author: iamaziz

torch/nn/modules/linear.py

@@ -84,7 +84,7 @@ class Bilinear(Module):
 
         >>> m = nn.Bilinear(20, 30, 40)
         >>> input1 = autograd.Variable(torch.randn(128, 20))
-        >>> input1 = autograd.Variable(torch.randn(128, 30))
+        >>> input2 = autograd.Variable(torch.randn(128, 30))
         >>> output = m(input1, input2)
         >>> print(output.size())
     """