hide the empty "set as default browser" groupbox on linux in the General pref panel

browser/components/prefwindow/content/unix/platformPrefOverlay.xul

@@ -1,33 +0,0 @@
-<?xml version="1.0"?>
-
-<!--
-   The contents of this file are subject to the Netscape Public
-   License Version 1.1 (the "License"); you may not use this file
-   except in compliance with the License. You may obtain a copy of
-   the License at http://www.mozilla.org/NPL/
-    
-   Software distributed under the License is distributed on an "AS
-   IS" basis, WITHOUT WARRANTY OF ANY KIND, either express or
-   implied. See the License for the specific language governing
-   rights and limitations under the License.
-    
-   The Original Code is Mozilla Communicator client code, released
-   March 31, 1998.
-   
-   The Initial Developer of the Original Code is Netscape
-   Communications Corporation. Portions created by Netscape are
-   Copyright (C) 1998-1999 Netscape Communications Corporation. All
-   Rights Reserved.
-   
-   Contributor(s): 
-     Ben Goodger <ben@netscape.com>
-  -->
-
-<!DOCTYPE window SYSTEM "chrome://communicator-platform/locale/pref/platformPrefOverlay.dtd">  
-  
-<overlay id="platformPreferencesOverlay"
-         xmlns="http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul">
-
-         
-</overlay>
-