[Bug libstdc++/120386] std::unique_copy uses the output type for comparisons

[redi at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=120386

--- Comment #4 from Jonathan Wakely <redi at gcc dot gnu.org> ---
https://cplusplus.github.io/LWG/issue4269 was opened to fix the standard to
match what real implementations do.