[WebRTC] Update WebRTC sources after 265320@main

https://bugs.webkit.org/show_bug.cgi?id=258208

Reviewed by Youenn Fablet.

* Source/ThirdParty/libwebrtc/CMakeLists.txt: Update WebRTC source
  files.
* Source/ThirdParty/libwebrtc/Source/webrtc/modules/video_coding/codecs/h264/h264_encoder_impl.cc:
  Re-introduce change from 236571@main

Canonical link: https://commits.webkit.org/265400@main

Author: dpino