message: Removing stale TODO.
  This was added a few years ago, and we ended up never
  serializing DELEGATE ops to model directly.
diff: @@ -667,7 +667,6 @@ TfLiteStatus ParseOpDataTfLite(const Operator* op, BuiltinOperator op_type,
  return kTfLiteOk;
  }
  case BuiltinOperator_DELEGATE: {
  - // TODO(ycling): Revisit when supporting saving delegated models.
  TF_LITE_REPORT_ERROR(error_reporter,
  "DELEGATE op shouldn't exist in model.");
  return kTfLiteError;
  