Post Processing Settings do not update in Persona when the values are changed in Preview Scene Settings

The post processing effects do not update in the Persona Viewport in realtime.

They will take effect if the post process setting is disabled and renabled.

This is a regression.

1. Open a skeletal mesh in Person
2. Click on Window -> Preview Scene Setting
3. Expand the Advanced options -> Post Processing Settings -> Color Grading
4. Enable Saturation
5. Change the values

Result: Post processing settings do not take effect

Expected: Post processing settings update when the values are modified