[class.pre] Fix incorrect comment in example

Author: jensmaurer

source/classes.tex

@@ -106,7 +106,7 @@
 }
 using N::A;
 template<class T> struct A<T>::B {};    // OK
-template<> struct A<void> {};           // error: \tcode{A} not nominable in \tcode{::}
+template<> struct A<void> {};           // OK
 \end{codeblock}
 \end{example}