[pairs.pair] Add missing _v for type traits (#5196)

Author: frederick-vs-ja

source/utilities.tex

@@ -932,9 +932,9 @@
 \constraints
 \begin{itemize}
 \item
-\tcode{is_copy_assignable<const T1>} is \tcode{true} and
+\tcode{is_copy_assignable_v<const T1>} is \tcode{true} and
 \item
-\tcode{is_copy_assignable<const T2>} is \tcode{true}.
+\tcode{is_copy_assignable_v<const T2>} is \tcode{true}.
 \end{itemize}
 
 \pnum
@@ -1032,9 +1032,9 @@
 \constraints
 \begin{itemize}
 \item
-\tcode{is_assignable<const T1\&, T1>} is \tcode{true} and
+\tcode{is_assignable_v<const T1\&, T1>} is \tcode{true} and
 \item
-\tcode{is_assignable<const T2\&, T2>} is \tcode{true}.
+\tcode{is_assignable_v<const T2\&, T2>} is \tcode{true}.
 \end{itemize}
 
 \pnum