No dropout, label smoothing, max_length.

def transformer_clean():
  """No dropout, label smoothing, max_length."""
  hparams = transformer_base_v2()
  hparams.label_smoothing = 0.0
  hparams.layer_prepostprocess_dropout = 0.0
  hparams.attention_dropout = 0.0
  hparams.relu_dropout = 0.0
  hparams.max_length = 0
  return hparams