Skip tst_MacNativeEvents::testChildDialogInFrontOfModalParent()

Closing the dialog at the end of the test ends the modal session via
QCocoaEventDispatcherPrivate::endModalSession(), but the actual ending
of the session is deferred to cleanupModalSessions(), and that is never called.

The result is that QCocoaWindow::setVisible of the window in testKeyPressOnToplevel
and following tests ends up calling [m_nsWindow orderFront:nil]; instead of
[m_nsWindow makeKeyAndOrderFront:nil];, leaving the window inactive and the
tests failing.

Task-number: QTBUG-58474
Change-Id: If66b2e201f658b627c2ec50a562938f59a5037ed
Reviewed-by: Tor Arne Vestbø <tor.arne.vestbo@qt.io>

tests/auto/other/macnativeevents/tst_macnativeevents.cpp

@@ -280,6 +280,8 @@ void tst_MacNativeEvents::testMouseEnter()
 
 void tst_MacNativeEvents::testChildDialogInFrontOfModalParent()
 {
+    QSKIP("Modal dialog causes later tests to fail, see QTBUG-58474");
+
     // Test that a child dialog of a modal parent dialog is
     // in front of the parent, and active:
     QDialog parent;