[Bug c++/94057] [9/10 Regression] -std=gnu++20 causes failure naming nested templated class since r9-4536

[mpolacek at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94057

--- Comment #5 from Marek Polacek <mpolacek at gcc dot gnu.org> ---
(We accept it when the template keyword is added: "typename A<T>::template
B<U>".)