LWG3816 flat_map and flat_multimap should impose sequence container requirements

Fixes NB US 103 (C++23 CD).

Author: burblebee

source/containers.tex

@@ -14621,10 +14621,12 @@
 \end{note}
 
 \pnum
-Any sequence container\iref{sequence.reqmts} \tcode{C}
-supporting \oldconcept{RandomAccessIterator} can be used
-to instantiate \tcode{flat_map},
-as long as invocations of
+Any type \tcode{C}
+that meets the sequence container requirements\iref{sequence.reqmts}
+can be used to instantiate \tcode{flat_map},
+as long as
+\tcode{C::iterator} meets the \oldconcept{RandomAccessIterator} requirements and
+invocations of
 member functions \tcode{C::size} and \tcode{C::max_size} do not exit via an exception.
 In particular, \tcode{vector}\iref{vector} and \tcode{deque}\iref{deque}
 can be used.
@@ -15763,10 +15765,12 @@
 \end{note}
 
 \pnum
-Any sequence container\iref{sequence.reqmts} \tcode{C}
-supporting \oldconcept{RandomAccessIterator} can be used to
-instantiate \tcode{flat_multimap},
-as long as invocations of
+Any type \tcode{C}
+that meets the sequence container requirements\iref{sequence.reqmts}
+can be used to instantiate \tcode{flat_multimap},
+as long as
+\tcode{C::iterator} meets the \oldconcept{RandomAccessIterator} requirements and
+invocations of
 member functions \tcode{C::size} and \tcode{C::max_size} do not exit via an exception.
 In particular,
 \tcode{vector}\iref{vector} and \tcode{deque}\iref{deque} can be used.