Remove chain of methods in RtpRtcp module to get current payload frequency for RTCP SRs

webrtc/modules/rtp_rtcp/source/rtp_sender_audio.cc

Index: webrtc/modules/rtp_rtcp/source/rtp_sender_audio.cc
diff --git a/webrtc/modules/rtp_rtcp/source/rtp_sender_audio.cc b/webrtc/modules/rtp_rtcp/source/rtp_sender_audio.cc
index 5dc82fc8fce2dfb6aeb504d537ada76088d4f8fc..63d27920380047d932141dfc1ba30c09a07e631b 100644
--- a/webrtc/modules/rtp_rtcp/source/rtp_sender_audio.cc
+++ b/webrtc/modules/rtp_rtcp/source/rtp_sender_audio.cc
@@ -50,10 +50,6 @@ RTPSenderAudio::RTPSenderAudio(Clock* clock, RTPSender* rtp_sender)
 
 RTPSenderAudio::~RTPSenderAudio() {}
 
-int RTPSenderAudio::AudioFrequency() const {
-  return kDtmfFrequencyHz;
-}
-
 // set audio packet size, used to determine when it's time to send a DTMF packet
 // in silence (CNG)
 int32_t RTPSenderAudio::SetAudioPacketSize(uint16_t packet_size_samples) {