XEP-0198: Fix example 12 by s/xml/xmlns/

This is a pure editorial change.

xep-0198.xml

@@ -376,7 +376,7 @@
 ]]></example>
   <p>If the server does not support session resumption, it MUST return a &lt;failed/&gt; element, which SHOULD include an error condition of &feature;. If the server does not recognize the 'previd' as an earlier session (e.g., because the former session has timed out), it MUST return a &lt;failed/&gt; element, which SHOULD include an error condition of &notfound;. If the server recogizes the 'previd' as an earlier session that has timed out the server MAY also include a 'h' attribute indicating the number of stanzas received before the timeout. (Note: For this to work the server has to store the SM-ID/sequence number tuple past the time out of the actual session.)</p>
   <example caption='Stream timed out'><![CDATA[
-<failed xml='urn:xmpp:sm:3'
+<failed xmlns='urn:xmpp:sm:3'
         h='another-sequence-number'>
   <item-not-found xmlns='urn:ietf:params:xml:ns:xmpp-stanzas'/>
 </failed>