[polymorphic.general] Fix garbled expression (#7820)

The applied paper P3019R14 had truncated text.

Author: xmcgcg

source/memory.tex

@@ -6633,7 +6633,7 @@
 \pnum
 Constructing an owned object of type \tcode{U} with \tcode{args...}
 using the allocator \tcode{a} means calling
-\tcode{allocator_traits<Allocator>::cop, args...)} where
+\tcode{allocator_traits<Allocator>::construct(a, \exposid{p}, args...)} where
 \tcode{args} is an expression pack,
 \tcode{a} is an allocator, and
 \exposid{p} points to storage suitable for an owned object of type \tcode{U}.