message: remove sentence about usage of rmsprop for RNN
diff: @@ -229,9 +229,6 @@ class RMSprop(Optimizer):
  at their default values
  (except the learning rate, which can be freely tuned).
  - This optimizer is usually a good choice for recurrent
  - neural networks.
  -
  Arguments:
  lr: float >= 0. Learning rate.
  rho: float >= 0.
  