Clean up in module_common_types.h by removing the unused struct RTPAudioHeader.

By removing it we can in turn (next CL) get rid of RTPTypeHeader, which is a
union that cause some problems.

Bug: none
Change-Id: I9246ecbfe2c8b7eda27497cccbc5f438958b64bf
Reviewed-on: https://webrtc-review.googlesource.com/83985
Reviewed-by: Stefan Holmer <stefan@webrtc.org>
Reviewed-by: Henrik Lundin <henrik.lundin@webrtc.org>
Commit-Queue: Philip Eliasson <philipel@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#23666}

modules/rtp_rtcp/include/rtp_receiver.h

@@ -101,9 +101,6 @@ class RtpReceiver {
   // Returns the current remote CSRCs.
   virtual int32_t CSRCs(uint32_t array_of_csrc[kRtpCsrcSize]) const = 0;
 
-  // Returns the current energy of the RTP stream received.
-  virtual int32_t Energy(uint8_t array_of_energy[kRtpCsrcSize]) const = 0;
-
   virtual std::vector<RtpSource> GetSources() const = 0;
 };
 }  // namespace webrtc