Fixup CWG2317: fix example as per email from Andrzej Krzemienski

Author: Dawn Perchik

source/declarations.tex

@@ -4827,7 +4827,7 @@
   A a{a,a};                     // OK
 
   struct B {
-    int n = B{}.m;              // error
+    int n = B{}.n;              // error
   };
 \end{codeblock}
 \end{example}