fix: exit animation of the application disappeared in treeland

When clicking the close button, call the widget::close.
Modify that calling dapplication::quit is the same as clicking the option to exit

Log:

src/widgets/dtitlebar.cpp

@@ -21,6 +21,7 @@
 #include <QScreen>
 #include <QWindow>
 #include <QActionGroup>
+#include <qnamespace.h>
 #include <qpa/qplatformwindow.h>
 
 #include "dpalettehelper.h"
@@ -1533,7 +1534,7 @@ void DTitlebar::setVisible(bool visible)
         connect(d->maxButton, SIGNAL(clicked()), this, SLOT(_q_toggleWindowState()), Qt::UniqueConnection);
         connect(this, SIGNAL(doubleClicked()), this, SLOT(_q_toggleWindowState()), Qt::UniqueConnection);
         connect(d->minButton, SIGNAL(clicked()), this, SLOT(_q_showMinimized()), Qt::UniqueConnection);
-        connect(d->closeButton, &DWindowCloseButton::clicked, d->targetWindow(), &QWidget::close, Qt::UniqueConnection);
+        connect(d->closeButton, SIGNAL(clicked(bool)), this, SLOT(_q_quitActionTriggered()), Qt::UniqueConnection);
 
         d->updateButtonsState(d->targetWindow()->windowFlags());
     } else {