UI: Disable multitrack video settings on non-win32 platforms

[palana]

Description

Disables multitrack video output settings for platforms other than windows

Motivation and Context

System info is not implemented for platforms other than windows, so the overall sentiment is/was to disable the multitrack video output for other platforms until system info is implemented (and ideally encoders for those other platforms are validated and/or encoder ladders/configs are available)

How Has This Been Tested?

Verified that these settings are available on windows builds, but aren't available on MacOS builds

Types of changes

• Tweak (non-breaking change to improve existing functionality)

Checklist:

• My code has been run through clang-format.
• I have read the contributing document.
• My code is not on the master branch.
• The code has been tested.
• All commit messages are properly formatted and commits squashed where appropriate.
• I have included updates to all appropriate documentation.

[derrod]

Seems fine as-is.