qt: update forgotten emit to Q_EMIT in macdockiconhandler.mm

Leftover from #6433

Rebased-From: ce183dce2e13c23ed279f4d9dae281e8e5977ebd

src/qt/macdockiconhandler.mm

@@ -130,5 +130,5 @@ void MacDockIconHandler::handleDockIconClickEvent()
         this->mainWindow->show();
     }
 
-    emit this->dockIconClicked();
+    Q_EMIT this->dockIconClicked();
 }