Minor fix to an error message from RNN
It appears to be a copy-paste error.
@@ -668,7 +668,7 @@ class RNN(Layer):
'a `batch_input_shape` '
'argument to your first layer.\n'
'- If using the functional API, specify '
- 'the time dimension by passing a '
+ 'the batch size by passing a '
'`batch_shape` argument to your Input layer.')
# initialize state if None
if self.states[0] is None:
