message: Fix incorrect doc in sparse_softmax_cross_entropy_with_logits
  This fix fixes the incorrect doc in sparse_softmax_cross_entropy_with_logits.
  In sparse_softmax_cross_entropy_with_logits, `labels` must be `int32` or `int64`,
  as is seen in:
  This fix fixes 21435.
diff: @@ -2003,8 +2003,8 @@ def sparse_softmax_cross_entropy_with_logits(
  A common use case is to have logits and labels of shape
  `[batch_size, num_classes]`, but higher dimensions are supported, in which
  case the `dim`-th dimension is assumed to be of size `num_classes`.
  - `logits` and `labels` must have the same dtype (either `float16`, `float32`,
  - or `float64`).
  + `logits` must have the dtype of `float16`, `float32`, or `float64`, and
  + `labels` must have the dtype of `int32` or `int64`.
  **Note that to avoid confusion, it is required to pass only named arguments to
  this function.**
  