Corrected doc in class RNNCell (pytorch#9866)

Summary:
fixes pytorch#9642
Pull Request resolved: pytorch#9866

Differential Revision: D9012131

Pulled By: weiyangfb

fbshipit-source-id: d2849b1a50234dbdb335dffab4835c9de85183c3

Author: weiyangfb

torch/nn/modules/rnn.py

@@ -579,7 +579,7 @@ class RNNCell(RNNCellBase):
 
     Attributes:
         weight_ih: the learnable input-hidden weights, of shape
-            `(input_size x hidden_size)`
+            `(hidden_size x input_size)`
         weight_hh: the learnable hidden-hidden weights, of shape
             `(hidden_size x hidden_size)`
         bias_ih: the learnable input-hidden bias, of shape `(hidden_size)`