[temp.variadic] Change "init-capture pack" to "init-capture pack declaration"

Author: xmh0511

source/templates.tex

@@ -2831,7 +2831,7 @@
 designating the variable introduced by
 the $i^\text{th}$ \grammarterm{init-capture}
 that resulted from instantiation of
-the \grammarterm{init-capture} pack.
+the \grammarterm{init-capture} pack declaration.
 \end{itemize}
 When $N$ is zero, the instantiation of a pack expansion
 does not alter the syntactic interpretation of the enclosing construct,