message: fix a bad requires clause in sample_view
diff: @@ -169,10 +169,11 @@ namespace ranges
  }
  template<bool Const = true>
  auto begin_cursor() const -> CPP_ret(cursor<Const>)( //
  - requires Const && sized_range<meta::const_if_c<Const, Rng>> ||
  + requires Const &&
  + (sized_range<meta::const_if_c<Const, Rng>> ||
  sized_sentinel_for<sentinel_t<meta::const_if_c<Const, Rng>>,
  iterator_t<meta::const_if_c<Const, Rng>>> ||
  - forward_range<meta::const_if_c<Const, Rng>>)
  + forward_range<meta::const_if_c<Const, Rng>>))
  {
  return cursor<true>{*this};
  }
  