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/interface/rtp_rtcp.h

@@ -487,13 +487,6 @@ class RtpRtcp : public Module {
     virtual void SetREMBData(uint32_t bitrate,
                              const std::vector<uint32_t>& ssrcs) = 0;
 
-    /*
-    *   (IJ) Extended jitter report.
-    */
-    virtual bool IJ() const = 0;
-
-    virtual void SetIJStatus(bool enable) = 0;
-
     /*
     *   (TMMBR) Temporary Max Media Bit Rate
     */