message: [tf.data] Fix some comment in dataset_ops.
diff: @@ -1792,7 +1792,7 @@ name=None))
  Args:
  map_func: A function mapping a dataset element to another dataset element.
  - num_parallel_calls: (Optional.) A `tf.int32` scalar `tf.Tensor`,
  + num_parallel_calls: (Optional.) A `tf.int64` scalar `tf.Tensor`,
  representing the number elements to process asynchronously in parallel.
  If not specified, elements will be processed sequentially. If the value
  `tf.data.AUTOTUNE` is used, then the number of parallel
  