[meta.reflection.queries] Add missing paragraph in is_{const,volatile}.

This was omitted in the application of P2996R13 by accident.

Author: tkoeppe

source/meta.tex

@@ -4239,6 +4239,10 @@
 \end{itemdecl}
 
 \begin{itemdescr}
+\pnum
+Let $T$ be \tcode{type_of(r)} if \tcode{\exposid{has-type}(r)} is \tcode{true}.
+Otherwise, let $T$ be \tcode{dealias(r)}.
+
 \pnum
 \returns
 \tcode{true} if \tcode{r} represents a const or volatile type, respectively,