UI: Fix memory leak in OBSQTDisplay

In my previous commit fd502cbd4, SurfaceEventFilter was not destroyed
and caused memory leaks.

UI/qt-display.cpp

@@ -17,7 +17,7 @@ class SurfaceEventFilter : public QObject {
 	OBSQTDisplay *display;
 
 public:
-	SurfaceEventFilter(OBSQTDisplay *src) : display(src) {}
+	SurfaceEventFilter(OBSQTDisplay *src) : QObject(src), display(src) {}
 
 protected:
 	bool eventFilter(QObject *obj, QEvent *event) override