Delete the VideoCodec::plName string.

It holds the same information as codecType, but in different format.

Bug: webrtc:8830
Change-Id: Ia83e2dff4fd9a5ddb489501b7a1fe80759fa4218
Reviewed-on: https://webrtc-review.googlesource.com/56100
Reviewed-by: Erik Språng <sprang@webrtc.org>
Reviewed-by: Karl Wiberg <kwiberg@webrtc.org>
Reviewed-by: Danil Chapovalov <danilchap@webrtc.org>
Commit-Queue: Niels Moller <nisse@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#22307}

modules/rtp_rtcp/include/rtp_rtcp.h

@@ -130,9 +130,6 @@ class RtpRtcp : public Module, public RtcpFeedbackSenderInterface {
   // Sets codec name and payload type. Returns -1 on failure else 0.
   virtual int32_t RegisterSendPayload(const CodecInst& voice_codec) = 0;
 
-  // Sets codec name and payload type. Return -1 on failure else 0.
-  virtual int32_t RegisterSendPayload(const VideoCodec& video_codec) = 0;
-
   virtual void RegisterVideoSendPayload(int payload_type,
                                         const char* payload_name) = 0;