SEC-1613: Corrected preauth docs.

docs/manual/src/docbook/preauth.xml

@@ -139,7 +139,7 @@
         <para> A typical configuration using this filter would look like this: <programlisting><![CDATA[
   <security:http>
     <!-- Additional http configuration omitted -->
-    <security:custom-filter ref="siteminderFilter" />
+    <security:custom-filter position="PRE_AUTH_FILTER" ref="siteminderFilter" />
   </security:http>
 
     <bean id="siteminderFilter" class=