message: fix bad constraint on iter_transform2_view::cursor::distance
diff: @@ -260,8 +260,8 @@ namespace ranges
  ranges::advance(it2_, n);
  }
  CONCEPT_REQUIRES(
  - SizedSentinel<iterator_t<R1>, iterator_t<R2>>() &&
  - SizedSentinel<iterator_t<R1>, iterator_t<R2>>())
  + SizedSentinel<iterator_t<R1>, iterator_t<R1>>() &&
  + SizedSentinel<iterator_t<R2>, iterator_t<R2>>())
  difference_type distance_to(cursor const &that) const
  {
  // Return the smallest distance (in magnitude) of any of the iterator
  