[mem.poly.allocator.mem] Fix syntax for variadic template declaration

Fixes NB JP 009

Author: jensmaurer

source/utilities.tex

@@ -11856,7 +11856,7 @@
 
 \indexlibrarymember{new_object}{polymorphic_allocator}%
 \begin{itemdecl}
-template<class T, class CtorArgs...>
+template<class T, class... CtorArgs>
   [[nodiscard]] T* new_object(CtorArgs&&... ctor_args);
 \end{itemdecl}