In my post I was not suggesting to remove the jumper. I was suggesting to keep the jumper and remove the connection between +5V pin of Arduino and 5V pin of the L298N.
If the jumper is in place, the L298N uses its own regulator to get 5V for the logic part of the board, directly from the Li-ion batteries. If you remove the jumper, then you need to provide 5V for the L298N logic. Only in this last case it makes sense to connect the +5V from Arduino to 5V of the L298N.