[unord.multimap.overview] Fix presentation of member types

As already done in de6b0e7 for unordered_map.

Author: jwakely

source/containers.tex

@@ -11916,8 +11916,9 @@
 It provides the operations described in the
 preceding requirements table for equivalent keys; that is, an \tcode{unordered_multimap}
 supports the \tcode{a_eq} operations in that table, not the \tcode{a_uniq} operations.
-For an \tcode{unordered_multimap<Key, T>} the \tcode{key type} is \tcode{Key}, the
-mapped type is \tcode{T}, and the value type is \tcode{pair<const Key, T>}.
+For an \tcode{unordered_multimap<Key, T>} the \tcode{key_type} is \tcode{Key},
+the \tcode{mapped_type} is \tcode{T},
+and the \tcode{value_type} is \tcode{pair<const Key, T>}.
 
 \pnum
 Subclause~\ref{unord.multimap} only describes operations on \tcode{unordered_multimap}