Delete support for has_internal_source

Bug: webrtc:12875
Change-Id: I9683e71e1fe5b24802033ffcb32a531ca685fc6f
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/179220
Commit-Queue: Niels Moller <nisse@webrtc.org>
Reviewed-by: Tommi <tommi@webrtc.org>
Reviewed-by: Harald Alvestrand <hta@webrtc.org>
Reviewed-by: Ilya Nikolaevskiy <ilnik@webrtc.org>
Cr-Commit-Position: refs/heads/main@{#35353}

api/video_codecs/video_encoder_factory.h

@@ -29,12 +29,6 @@ class VideoEncoderFactory {
  public:
   // TODO(magjed): Try to get rid of this struct.
   struct CodecInfo {
-    // `has_internal_source` is true if encoders created by this factory of the
-    // given codec will use internal camera sources, meaning that they don't
-    // require/expect frames to be delivered via webrtc::VideoEncoder::Encode.
-    // This flag is used as the internal_source parameter to
-    // webrtc::ViEExternalCodec::RegisterExternalSendCodec.
-    bool has_internal_source = false;
   };
 
   struct CodecSupport {