SoftBody is not affected by space override

[bmolyneaux]

Godot version:
3.2

OS/device including version:
Windows 10

Issue description:
Area nodes have a space override which allows the gravity to be replaced. It works for RigidBody, but not for SoftBody.

Steps to reproduce:

1. Create a SoftBody within an Area.
2. Set the Area's Space Override to Replace and change its Gravity Vec.
3. The SoftBody will not be affected by the Area's overrides.

Minimal reproduction project:
This example project has a RigidBody and a SoftBody. The RigidBody falls to the right because of the Area's gravity override, but the SoftBody falls down.
SoftBodyBug.zip

[WilliamTambellini]

@Chaosus Coud that one be tagged for 4.0 ?