Cleanup unused function

Signed-off-by: falkTX <falktx@falktx.com>

dgl/src/WindowPrivateData.hpp

@@ -155,7 +155,6 @@ struct Window::PrivateData : IdleCallback {
     void onPuglMouse(const Events::MouseEvent& ev);
     void onPuglMotion(const Events::MotionEvent& ev);
     void onPuglScroll(const Events::ScrollEvent& ev);
-    void onPuglTimer(IdleCallback* idleCallback);
 
     // Pugl event handling entry point
     static PuglStatus puglEventCallback(PuglView* view, const PuglEvent* event);