Additional Qt keyword conversion. (#299)

This comit is an addtion to pull request #295. Not all Qt keywords were included.

Co-authored-by: Walter Bormans <walter.bormans@paradoxcat.com>

src/FloatingDragPreview.cpp

@@ -60,7 +60,7 @@ struct FloatingDragPreviewPrivate
 	void cancelDragging()
 	{
 		Canceled = true;
-		emit _this->draggingCanceled();
+		Q_EMIT _this->draggingCanceled();
 		DockManager->containerOverlay()->hideOverlay();
 		DockManager->dockAreaOverlay()->hideOverlay();
 		_this->close();