SEC-1839: Updated preauth example to use </security:authentication-manager> instead of </security-authentication-manager>

docs/manual/src/docbook/preauth.xml

@@ -160,7 +160,7 @@ class="org.springframework.security.web.authentication.preauth.PreAuthenticatedA
 
     <security:authentication-manager alias="authenticationManager">
       <security:authentication-provider ref="preauthAuthProvider" />
-    </security-authentication-manager>
+    </security:authentication-manager>
 ]]>
 </programlisting> We've assumed here that the security namespace is being used for
           configuration (hence the user of the <literal>custom-filter</literal>,