True Top-Down 2D 1.16.1 Update

I made a small update to the True Top-Down 2D series: Line2D points are now accessed via method calls. We used to directly go to the points array, but that property now creates copies of the underlying packed array.

This affects the series starting from tutorial 13 Coveyors. From that point on the tutorials are now made with Godot 4.7.