Delete method ModuleRtpRtcpImpl::SendPayloadType.

This was a trivial delegation wrapper, with only a single use.

BUG=None

Review-Url: https://codereview.webrtc.org/2741413003
Cr-Commit-Position: refs/heads/master@{#17205}

webrtc/modules/rtp_rtcp/source/rtp_rtcp_impl.h

@@ -57,8 +57,6 @@ class ModuleRtpRtcpImpl : public RtpRtcp, public RTCPReceiver::ModuleRtpRtcp {
 
   int32_t DeRegisterSendPayload(int8_t payload_type) override;
 
-  int8_t SendPayloadType() const;
-
   // Register RTP header extension.
   int32_t RegisterSendRtpHeaderExtension(RTPExtensionType type,
                                          uint8_t id) override;