Delete RtpData::OnRecoveredPacket, use RecoveredPacketReceiver instead.

BUG=webrtc:7135

Review-Url: https://codereview.webrtc.org/2886813002
Cr-Commit-Position: refs/heads/master@{#18305}

webrtc/modules/rtp_rtcp/include/flexfec_receiver.h

@@ -23,16 +23,6 @@
 
 namespace webrtc {
 
-// Callback interface for packets recovered by FlexFEC. The implementation
-// should be able to demultiplex the recovered RTP packets based on SSRC.
-class RecoveredPacketReceiver {
- public:
-  virtual void OnRecoveredPacket(const uint8_t* packet, size_t length) = 0;
-
- protected:
-  virtual ~RecoveredPacketReceiver() = default;
-};
-
 class FlexfecReceiver {
  public:
   FlexfecReceiver(uint32_t ssrc,