message: Remove incorrect comment related to `logits_input`.
diff: @@ -147,7 +147,6 @@ class _Head(object):
  """Returns `EstimatorSpec` that a model_fn can return.
  Please note that,
  - + Exactly one of `logits` and `logits_input` must be provided.
  + All args must be passed via name.
  Args:
  