Removed unused function declaration

src/video/SDL_sysvideo.h

@@ -583,7 +583,6 @@ extern SDL_Window *SDL_GetToplevelForKeyboardFocus(void);
 extern bool SDL_ShouldAllowTopmost(void);
 
 extern void SDL_ToggleDragAndDropSupport(void);
-extern void SDL_UpdateRawMouseDataEnabled(void);
 
 extern SDL_TextInputType SDL_GetTextInputType(SDL_PropertiesID props);
 extern SDL_Capitalization SDL_GetTextInputCapitalization(SDL_PropertiesID props);