[Bug c++/104760] Attribute [[deprecated]] causes diagnostic in never-instantiated template

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104760

--- Comment #5 from Jonathan Wakely <redi at gcc dot gnu.org> ---
Libstdc++ has the attribute on both of these templates. I used diagnostic
pragmas to stop the function templates from warning about the use of the class
templates.

If other code refers to either of them, it gets a warning. But the use of
unary_negate within std::not1 doesn't give a warning.