Removed extended jitter report from RtcpSender.

This was never used (value always 0, when sent)

BUG=2450
R=asapersson@webrtc.org

Review URL: https://codereview.webrtc.org/1208843003 .

Cr-Commit-Position: refs/heads/master@{#9631}

webrtc/modules/rtp_rtcp/source/rtp_rtcp_impl.h

@@ -191,11 +191,6 @@ class ModuleRtpRtcpImpl : public RtpRtcp {
   void SetREMBData(uint32_t bitrate,
                    const std::vector<uint32_t>& ssrcs) override;
 
-  // (IJ) Extended jitter report.
-  bool IJ() const override;
-
-  void SetIJStatus(bool enable) override;
-
   // (TMMBR) Temporary Max Media Bit Rate.
   bool TMMBR() const override;