Proposal: Remove "Frameworks compiler requirements and Modern C++" from Policies

[David Redondo]

> AFAICS we broke since we require C++20 since KF 6.13

Hmm I think I read and remembered it wrong it says

> C++: support the last two standard releases, this likely means C++20 for KF6.0

Last two would mean c++20 and c++23 right now

and with c++26 released we could start thinking about bumping to 23

David