Fix empty parameter section of XMLWriter::openMemory()

Author: ndossche

reference/xmlwriter/xmlwriter/openmemory.xml

@@ -25,8 +25,7 @@
  </refsect1>
  <refsect1 role="parameters">
   &reftitle.parameters;
-  <para>
-  </para>
+  &no.function.parameters;
  </refsect1>
 
  <refsect1 role="returnvalues">