message: [tf.data] document update to correct the non-working example.
diff: @@ -45,7 +45,7 @@ class StatsAggregator(object):
  # Apply `StatsOptions` to associate `dataset` with `aggregator`.
  options = dataset_ops.Options()
  - options.experimental_stats = tf.data.experimental.StatsOptions(aggregator)
  + options.experimental_stats.aggregator = aggregator
  dataset = dataset.with_options(options)
  ```
  