message: fix is_valid function for sig_figs
diff: @@ -22,7 +22,7 @@ class arg_output_sig_figs : public int_argument {
  _value = _default_value;
  }
  - bool is_valid(int value) { return value >= 0 || value == _default_value; }
  + bool is_valid(int value) { return (value >= 0 && value <= 18) || value == _default_value; }
  };
  } // namespace cmdstan
  