Subsurface shading model is broken when ray traced shadows are used in 5.1+

1. Create a new basic level.
2. Create a material with subsurface shading model.
3. Create a sphere static mesh in the scene with the material.
4. In project setting toggle on/off `Ray Traced Shadows`.

Expected: Ray traced shadow has smooth falloff

Actual: Ray traced shadow has a harsh cutoff.