This is a follow-up on #23460. Since OBS uses NV12 internally, it's better to capture in NV12 to avoid unnecessary conversions on the OBS side. This also removes the YUY2 implementation changes in #23460 that were specific to the OBS Virtual Camera.

Pull Request Readiness Checklist

See details at https://github.com/opencv/opencv/wiki/How_to_contribute#making-a-good-pull-request

• I agree to contribute to the project under Apache 2 License.
• To the best of my knowledge, the proposed patch is not based on a code under GPL or another license that is incompatible with OpenCV
• The PR is proposed to the proper branch
• There is a reference to the original bug report and related work
• The feature is well documented and sample code can be built with the project CMake