message: Fix deprecated use of `sparse_to_dense`.
  Calling `sparse_to_dense` gives a deprecation warning that asks users to use `sparse.to_dense`:
  However, `sparse.to_dense` calls `sparse_to_dense`, which again produces the deprecation warning.
diff: @@ -1422,7 +1422,7 @@ def sparse_tensor_to_dense(sp_input,
  """
  sp_input = _convert_to_sparse_tensor(sp_input)
  - return sparse_to_dense(
  + return gen_sparse_ops.sparse_to_dense(
  sp_input.indices,
  sp_input.dense_shape,
  sp_input.values,
  