If you have looked and it is not a usb connector then it most likely a connector for a battery charger. So if the scooter was not going to be used for a while you could connect a charger to it so the battery level would not go flat after sitting for a while. One of the local bike shops does that to all of their floor stock as it is a simple procedure. It looks like it has a built in fuse as well so it would have been done right and it would not have caused any problems. As others have suggested, just leave it off.