Remove dead code

Change-Id: I4ece8a94c1ce8cac65fb1d90bb18267e22a4ea7a
Reviewed-by: Simon Hausmann <simon.hausmann@qt.io>
Reviewed-by: Marc Mutz <marc.mutz@kdab.com>

src/plugins/platforms/cocoa/qt_mac_p.h

@@ -90,22 +90,6 @@ public:
     }
 };
 
-class Q_WIDGETS_EXPORT QMacWindowChangeEvent
-{
-private:
-    static QList<QMacWindowChangeEvent*> *change_events;
-public:
-    QMacWindowChangeEvent() {
-    }
-    virtual ~QMacWindowChangeEvent() {
-    }
-    static inline void exec(bool ) {
-    }
-protected:
-    virtual void windowChanged() = 0;
-    virtual void flushWindowChanged() = 0;
-};
-
 class QMacCGContext
 {
     CGContextRef context;