Fix XML markup

Move CData into <member> tag

Author: Girgias

appendices/migration84/new-classes.xml

@@ -70,7 +70,7 @@
   <title>PCNTL</title>
   <simplelist>
    <!-- Should this use <enumname> ? -->
-   <member><classname>Pcntl\QosClass</classname></member> (macOS only)
+   <member><classname>Pcntl\QosClass</classname> (macOS only)</member>
   </simplelist>
  </sect2>