[Bug libstdc++/120997] std::span::subspan returns initializer list

[redi at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=120997

--- Comment #2 from Jonathan Wakely <redi at gcc dot gnu.org> ---
The libstdc++ implementation follows the C++26 draft standard exactly:

  Effects: Equivalent to: return {data(), count};

So maybe we need to fix that.