[tab:meta.trans.cv] Simplify wording for add_{const,volatile}

Wording about reference, function, or top-level cv-qualified types
moves to notes, as it is redundant since at least C++11.

Author: frederick-vs-ja

source/meta.tex

@@ -1712,16 +1712,22 @@
 \indexlibraryglobal{add_const}%
 \tcode{template<class T>\br
  struct add_const;}                 &
- If \tcode{T} is a reference, function, or top-level const-qualified
- type, then \tcode{type} denotes \tcode{T}, otherwise
- \tcode{T const}.                                                           \\  \rowsep
+ The member typedef \tcode{type} denotes \tcode{const T}.
+\begin{tailnote}
+\keyword{const} has no effect when \tcode{T} is a reference, function, or
+top-level const-qualified type.
+\end{tailnote}
+\\ \rowsep
 
 \indexlibraryglobal{add_volatile}%
 \tcode{template<class T>\br
  struct add_volatile;}                  &
- If \tcode{T} is a reference, function, or top-level volatile-qualified
- type, then \tcode{type} denotes \tcode{T}, otherwise
- \tcode{T volatile}.                                                            \\  \rowsep
+ The member typedef \tcode{type} denotes \tcode{volatile T}.
+\begin{tailnote}
+\keyword{volatile} has no effect when \tcode{T} is a reference, function, or
+top-level volatile-qualified type.
+\end{tailnote}
+\\ \rowsep
 
 \indexlibraryglobal{add_cv}%
 \tcode{template<class T>\br