QCocoaApplicationDelegate: Remove unused function

This seems to be a leftover from pre-QPA Cocoa menus time.

Change-Id: I1bcfb3a882f500a63a5dec0fbe01f4541e14d54a
Reviewed-by: James Turner <james.turner@kdab.com>
Reviewed-by: Erik Verbruggen <erik.verbruggen@qt.io>
Reviewed-by: Timur Pocheptsov <timur.pocheptsov@theqtcompany.com>

src/plugins/platforms/cocoa/qcocoaapplicationdelegate.mm

@@ -445,10 +445,4 @@ QT_END_NAMESPACE
     [NSApp terminate:self];
 }
 
-- (void)qtDispatcherToQAction:(id)sender
-{
-    Q_UNUSED(sender);
-    [[self menuLoader] qtDispatcherToQPAMenuItem:sender];
-}
-
 @end