message: Update MultiWorkerMirroredStrategy.cluster_resolver's docstring as it's no longer experimental.
diff: @@ -207,11 +207,10 @@ class CollectiveAllReduceStrategy(distribute_lib.Strategy):
  def cluster_resolver(self):
  """Returns the cluster resolver associated with this strategy.
  - As a multi-worker strategy,
  - `tf.distribute.experimental.MultiWorkerMirroredStrategy` provides the
  - associated `tf.distribute.cluster_resolver.ClusterResolver`. If the user
  - provides one in `__init__`, that instance is returned; if the user does
  - not, a default `TFConfigClusterResolver` is provided.
  + As a multi-worker strategy, `tf.distribute.MultiWorkerMirroredStrategy`
  + provides the associated `tf.distribute.cluster_resolver.ClusterResolver`. If
  + the user provides one in `__init__`, that instance is returned; if the user
  + does not, a default `TFConfigClusterResolver` is provided.
  """
  return self.extended._cluster_resolver # pylint: disable=protected-access
  