Bug 106053, remove unused XHTML namespace declarations, and fix incorrect namespace usages. r=harishd, sr=hewitt.

suite/common/pref/preftree.xul

@@ -28,7 +28,6 @@
 <!DOCTYPE window SYSTEM "chrome://communicator/locale/pref/preftree.dtd" >
 
 <overlay id="prefTreeOverlay"
-  xmlns:html="http://www.w3.org/1999/xhtml"
   xmlns="http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul">
 
 <script>