Don't set window decorations

This works ootb with recent GTK versions now.
The workaround we used creates problems when run in HiDPI
(the window is misplaced and its size is twice larger).

usr/lib/linuxmint/mintMenu/mintMenu.py

@@ -57,9 +57,6 @@ class MainWindow( object ):
         builder = Gtk.Builder()
         builder.add_from_file(os.path.join( self.path, "mintMenu.glade" ))
         self.window     = builder.get_object( "mainWindow" )
-        self.window.realize()
-        self.window.get_window().set_decorations(Gdk.WMDecoration.BORDER)
-        self.window.set_title("")
         self.paneholder = builder.get_object( "paneholder" )
 
         builder.connect_signals(self)