message: remove out-of-date workaround for CartesianProductViewCanBidi
diff: @@ -101,12 +101,10 @@ namespace ranges
  (
  template(typename IsConst, typename...Views)
  (concept CartesianProductViewCanBidi)(IsConst, Views...),
  - // BUGBUG alternation is totally broken.
  - Type<> &&
  - (CartesianProductViewCanRandom<IsConst, Views...> ||
  + CartesianProductViewCanRandom<IsConst, Views...> ||
  And<CommonRange<meta::const_if<IsConst, Views>>...,
  BidirectionalIterator<iterator_t<
  - meta::const_if<IsConst, Views>>>...>)
  + meta::const_if<IsConst, Views>>>...>
  );
  template<typename... Views>
  