[Bug c/84258] Bogus -Wformat warning "wide character string" for const unsigned char

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=84258

--- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Should most likely say the format is not of an array of char type.  Note I bet
it will also warn about signed char too.