UI: Removed unused friend classes

[Tunghohin]

Description

The class DeviceToolbarPropertiesThread appears to have been removed, and the friend class here is redundant code

Motivation and Context

The class is located in

but has been removed in 50d3130.

How Has This Been Tested?

Yes, on windows11-22H2.

Types of changes

Clean up code.

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.

[norihiro]

Another class TwitchLogin is not found as well. Can we remove it at the same time?

obs-studio/UI/auth-twitch.hpp

Line 16 in f60d6bc

friend class TwitchLogin;

[RytoEX]

Do not use merge commits to catch up on commit history. Use git rebase.