-Unable to add more than one Sky & RayTracing overrides in Sky & Fog Volume.
-On trying to add more than one overrides it throws ArgumentException error and remove previously added override.
-ArgumentException error is thrown on adding Sky & RayTracings overrides.

Steps to repro:
1. Create a new HDRP template project
2. Hierarchy > Sky & Fog Volume > Inspector.
3. Add Override >Sky > Gradient Sky.
4. Add Override >Sky > Physical Based Sky.

Actual Result:
ArgumentException error is thrown in the console.

Expected Result:
No error in the console.

Reproducible in:
2020.2.0a18, 2020.1.0b16 with 8.2.0

Working Fine in:
2020.2.0a18 With Package Version 9.0.0, 8.1.0.

Environment:
Occurring only on Windows 10.

Note: Refer attached stacktrace.