Remove wxRTTI macros from wxSpinCtrlGTKBase.

This is not a public class and it doesn't need to be appear in wxRTTI.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@72411 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

include/wx/gtk/spinctrl.h

@@ -79,7 +79,6 @@ protected:
     // override this and return true.
     virtual bool UseGTKStyleBase() const { return true; }
 
-    DECLARE_DYNAMIC_CLASS(wxSpinCtrlGTKBase)
     DECLARE_EVENT_TABLE()
 };