Fix to CWG1662.

Add missing parentheses around reference.

Author: Stefanus Du Toit

source/templates.tex

@@ -1952,7 +1952,7 @@
 \begin{itemize}
 \item
 if the pack is a template parameter pack, the element is a template
-parameter~\ref{temp.param} of the corresponding kind (type or
+parameter~(\ref{temp.param}) of the corresponding kind (type or
 non-type) designating the type or value from the template
 argument; otherwise,