Reference class for attribute

Co-authored-by: Christoph M. Becker <[email protected]>

Author: Girgias

language/oop5/basic.xml

@@ -136,7 +136,7 @@ Stack trace:
      and prevent the creation of
      <link linkend="language.oop5.properties.dynamic-properties">dynamic properties</link>.
      Moreover, it is impossible to add support for them by using the
-     <code>#[AllowDynamicProperties]</code> attribute. Attempting to do so
+     <classname>AllowDynamicProperties</classname> attribute. Attempting to do so
      will trigger a compile-time error.
     </para>
     <example>