[0.13.20] Minor transport belt / car physics issue

[SupplyDepoo]

When a car is moving while on top of transport belts, it can jitter back and forward a bit.

It's not gamebraking but it's very noticeable when the car is decelerating at slow speeds.

Video: https://gfycat.com/GiddyLightheartedGreathornedowl

Steps to reproduce:

1. Set up two parallel transport belts 6–10 tiles long.
2. Drive a car very slowly onto the belts.

Additional notes:

1. Tested in singleplayer only.
2. Tested with yellow & red belts only.
3. Tested with car only.
4. Also happens while reversing onto the belts, but less pronounced.
5. Also happens if you drive perpendicular to the belts' direction.

[Rseding91]

That's just an unfortunate effect of how non-items are moved by belts. There's not much that can be done.

Personally I'd like to just remove the belts-move-non-items mechanic from the game as it would also save CPU time not having to do that logic.