message: [tf.data] Modernize description of using datasets with estimators.
diff: @@ -782,8 +782,9 @@ with tf.train.MonitoredTrainingSession(...) as sess:
  sess.run(training_op)
  ```
  -To use a `Dataset` in the `input_fn` of a `tf.estimator.Estimator`, we also
  -recommend using `Dataset.make_one_shot_iterator()`. For example:
  +To use a `Dataset` in the `input_fn` of a `tf.estimator.Estimator`, simply
  +return the `Dataset` and the framework will take care of creating an iterator
  +and initializing it for you. For example:
  ```python
  def dataset_input_fn():
  @@ -814,10 +815,9 @@ def dataset_input_fn():
  dataset = dataset.shuffle(buffer_size=10000)
  dataset = dataset.batch(32)
  dataset = dataset.repeat(num_epochs)
  - iterator = dataset.make_one_shot_iterator()
  - # `features` is a dictionary in which each value is a batch of values for
  - # that feature; `labels` is a batch of labels.
  - features, labels = iterator.get_next()
  - return features, labels
  + # Each element of `dataset` is tuple containing a dictionary of features
  + # (in which each value is a batch of values for that feature), and a batch of
  + # labels.
  + return dataset
  ```
  