Delete RtcpStatistic struct as no longer used

Bug: webrtc:10678
Change-Id: Ic99910817f8b3044124a212627f0a754a54b69e7
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/219284
Reviewed-by: Erik Språng <sprang@webrtc.org>
Commit-Queue: Danil Chapovalov <danilchap@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#34046}

modules/rtp_rtcp/include/rtcp_statistics.h

diff --git a/modules/rtp_rtcp/include/rtcp_statistics.h b/modules/rtp_rtcp/include/rtcp_statistics.h
index 8a63324..de70c14 100644
--- a/modules/rtp_rtcp/include/rtcp_statistics.h
+++ b/modules/rtp_rtcp/include/rtcp_statistics.h
@@ -17,16 +17,6 @@
 
 namespace webrtc {
 
-// Statistics for an RTCP channel
-// TODO(bugs.webrtc.org/10678): Remove remaining usages of this struct in favor
-// of RTCPReportBlock, rtcp::ReportBlock or other similar structs.
-struct RtcpStatistics {
-  uint8_t fraction_lost = 0;
-  int32_t packets_lost = 0;  // Defined as a 24 bit signed integer in RTCP
-  uint32_t extended_highest_sequence_number = 0;
-  uint32_t jitter = 0;
-};
-
 // Statistics for RTCP packet types.
 struct RtcpPacketTypeCounter {
   RtcpPacketTypeCounter()