[allocator.requirements.general] Fix missing ellipsis (#6695)

Author: lewissbaker

source/lib-intro.tex

@@ -2572,7 +2572,7 @@
 \end{itemdescr}
 
 \begin{itemdecl}
-a.construct(c, args)
+a.construct(c, args...)
 \end{itemdecl}
 
 \begin{itemdescr}