message: Fix typo: SyncReplicaOptimizer -> SyncReplicasOptimizer
diff: @@ -449,7 +449,7 @@ class _SyncReplicasOptimizerHook(session_run_hook.SessionRunHook):
  """A SessionRunHook handles ops related to SyncReplicasOptimizer."""
  def __init__(self, sync_optimizer, is_chief, num_tokens):
  - """Creates hook to handle SyncReplicaOptimizer initialization ops.
  + """Creates hook to handle SyncReplicasOptimizer initialization ops.
  Args:
  sync_optimizer: `SyncReplicasOptimizer` which this hook will initialize.
  