Delete telephone-event handling from RTPReceiverAudio.

Bug: webrtc:7135
Change-Id: Ic8b96f44ba25ff9265570dd43d3c76ed0177abfb
Reviewed-on: https://webrtc-review.googlesource.com/91125
Reviewed-by: Oskar Sundbom <ossu@webrtc.org>
Reviewed-by: Åsa Persson <asapersson@webrtc.org>
Commit-Queue: Niels Moller <nisse@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#24172}

modules/rtp_rtcp/include/rtp_receiver.h

@@ -25,10 +25,6 @@ class TelephoneEventHandler {
  public:
   virtual ~TelephoneEventHandler() {}
 
-  // The following three methods implement the TelephoneEventHandler interface.
-  // Forward DTMFs to decoder for playout.
-  virtual void SetTelephoneEventForwardToDecoder(bool forward_to_decoder) = 0;
-
   // Is TelephoneEvent configured with payload type payload_type
   virtual bool TelephoneEventPayloadType(const int8_t payload_type) const = 0;
 };