pythongh-112898: Fix double close dialog with warning about unsafed f…

…iles

Without this changeset I get two consecutive dialogs asking
if I want to save an unsafed file, when choosing "Cancel" in the
first one.

Lib/idlelib/macosx.py

@@ -221,7 +221,7 @@ def help_dialog(event=None):
         # The binding above doesn't reliably work on all versions of Tk
         # on macOS. Adding command definition below does seem to do the
         # right thing for now.
-        root.createcommand('::tk::mac::Quit', flist.close_all_callback)
+        root.createcommand('::tk::mac::Quit', lambda: "break")
 
     if isCarbonTk():
         # for Carbon AquaTk, replace the default Tk apple menu