Remove Qt::Widgets dependency

[sandboxcoder]

Motivation for change

Removing Qt6 dependency that I inadvertantly merged from obs-30.2. Adding comment we do not need to enable Qt::Widgets.

Now when I run otool -L on the obs-browser.plugin for mac it no longer depends on Qt framework:

~/projects/streamlabs/obs-studio/build_macos/UI/RelWithDebInfo/OBS.app/Contents/PlugIns/obs-browser.plugin/Contents/MacOS/obs-browser:
	/System/Library/Frameworks/AppKit.framework/Versions/C/AppKit (compatibility version 45.0.0, current version 2575.50.26)
	/System/Library/Frameworks/CoreFoundation.framework/Versions/A/CoreFoundation (compatibility version 150.0.0, current version 3423.0.0)
	@rpath/libobs.framework/Versions/A/libobs (compatibility version 1.0.0, current version 30.0.0)
	@rpath/obs-frontend-api.dylib (compatibility version 1.0.0, current version 30.0.0)
	/System/Library/Frameworks/Foundation.framework/Versions/C/Foundation (compatibility version 300.0.0, current version 3423.0.0)
	/usr/lib/libobjc.A.dylib (compatibility version 1.0.0, current version 228.0.0)
	/usr/lib/libc++.1.dylib (compatibility version 1.0.0, current version 1900.178.0)
	/usr/lib/libSystem.B.dylib (compatibility version 1.0.0, current version 1351.0.0)