message: Fix typos in ftrl.
diff: @@ -225,9 +225,9 @@ class Ftrl(optimizer_v2.OptimizerV2):
  'learning_rate_power':
  self._serialize_hyperparameter('learning_rate_power'),
  'l1_regularization_strength':
  - self._serializer_hyperparameter('l1_regularization_strength'),
  + self._serialize_hyperparameter('l1_regularization_strength'),
  'l2_regularization_strength':
  - self._serializer_hyperparameter('l2_regularization_strength'),
  + self._serialize_hyperparameter('l2_regularization_strength'),
  'l2_shrinkage_regularization_strength':
  self._l2_shrinkage_regularization_strength,
  })
  