QDefaultAnimationDriver: don't promote timerEvent() to public

Leave it as protected. Private API, so no BC constraints apply.

Change-Id: I876456a05372c9d3b83cb7a6410eeaa6c44f1d52
Reviewed-by: Volker Hilsheimer <volker.hilsheimer@qt.io>

src/corelib/animation/qabstractanimation_p.h

@@ -118,6 +118,8 @@ class QDefaultAnimationDriver : public QAnimationDriver
     Q_OBJECT
 public:
     QDefaultAnimationDriver(QUnifiedTimer *timer);
+
+protected:
     void timerEvent(QTimerEvent *e) override;
 
 private Q_SLOTS: