[Bug libstdc++/104098] [11/12 Regression] bits/stl_iterator.h fails to compile for __cplusplus > 201703L and with __cpp_concepts undefined

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104098

--- Comment #5 from Jonathan Wakely <redi at gcc dot gnu.org> ---
Fixed for trunk, backport to follow.