Removing incorrect XXX comments.

browser/base/content/browser.js

@@ -3448,8 +3448,6 @@ nsBrowserContentListener.prototype =
         // hook up the whole parent chain thing
         var windowDocShell = this.convertWindowToDocShell(toplevelWindow);
         if (windowDocShell) {
-            // XXXbz this listener is never unregistered.  Did someone neglect 
-            // to read the interface they're using?
             windowDocshell
               .QueryInterface(Components.interfaces.nsIInterfaceRequestor)
               .getInterface(Components.interfaces.nsIURIContentListener)

extensions/help/resources/content/help.js

@@ -140,7 +140,6 @@ function init() {
   helpGlossaryPanel = document.getElementById("help-glossary-panel");
   helpBrowser = document.getElementById("help-content");
   helpExternal = document.getElementById("help-external");
-  // XXXbz this is never unset.  That should be fixed.  See the IDL.
   helpExternal
     .docShell
     .QueryInterface(Components.interfaces.nsIInterfaceRequestor)

xpfe/browser/resources/content/nsBrowserContentListener.js

@@ -60,8 +60,6 @@ nsBrowserContentListener.prototype =
         // hook up the whole parent chain thing
         var windowDocShell = this.convertWindowToDocShell(toplevelWindow);
         if (windowDocShell) {
-            // XXXbz this listener is never unregistered.  Did someone neglect 
-            // to read the interface they're using?
             windowDocshell
               .QueryInterface(Components.interfaces.nsIInterfaceRequestor)
               .getInterface(Components.interfaces.nsIURIContentListener)