message: Fix broken link of performance guide for the `tf.data` API
diff: @@ -78,7 +78,7 @@ training CIFAR-10 illustrates the use of the `tf.data` API along with
  The `tf.data` API utilizes C++ multi-threading and has a much lower overhead
  than the Python-based `queue_runner` that is limited by Python's multi-threading
  performance. A detailed performance guide for the `tf.data` API can be found
  -[here](#datasets_performance).
  +[here](@{$datasets_performance}).
  While feeding data using a `feed_dict` offers a high level of flexibility, in
  general `feed_dict` does not provide a scalable solution. If only a single GPU
  