message: Remove _sentinel from v2 upgrade in sparse_softmax_cross_entropy_with_logits
diff: @@ -443,9 +443,6 @@ class TFAPIChangeSpec(ast_edits.APIChangeSpec):
  "tf.nn.weighted_cross_entropy_with_logits": {
  "targets": "labels",
  },
  - "tf.nn.sparse_softmax_cross_entropy_with_logits": {
  - "_sentinel": None,
  - },
  }
  # pylint: disable=line-too-long
  