On changing the Audio default speaker mode to "Raw" it sets as "Mono".

Steps to repro:
1. Open a new project.
2. Edit > Settings
3. Select Audio from the left panel.
4. In the right panel change the "Default Speaker Mode" to "Raw".

Actual Result:
"Default Speaker Mode" set to "Mono".

Expected Result:
"Default Speaker Mode" should set to "Raw".

Reproducible on:
2018.3.0a5, 2018.3.0a4

Note: Unified settings are introduced in 2018.3.0a4.

Environment:
Occurring on Windows and Mac