#11 Gravity modifier causing karts to stick to side of things

[Pyritie]

Usually ends up being the treehouse due to the "ramp" right before it.

Basically once we get the invisible wall/ceiling mesh up, we can reuse the Wall collision group and change it to Road or something. Then change the gravity modifier so it only works when we're driving on something classified as the road (the track, the grass, the cliff, the bridge, and the ramp) and not everything classified as Environment.