[committed] libstdc++: Fix std::variant to reject array types [PR116381]

[Jonathan Wakely]

On Wed, 21 Aug 2024 at 09:55, Jonathan Wakely wrote:
>
> Tested x86_64-linux. Pushed to trunk.
>
> Probably worth backporting too. It could potentially cause new errors
> for people using arrays in std::variant, but that's forbidden by the
> standard.

Notably, both libc++ and MSVC STL reject array types in std::variant.
Only libstdc++ had the bug that allowed them.