Delete deprecated method StreamStatistician::GetStatistics

Bug: webrtc:10679
Change-Id: I9374b390783ef557c6981d8b3cea0be71f58cd27
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/150323
Reviewed-by: Danil Chapovalov <danilchap@webrtc.org>
Commit-Queue: Niels Moller <nisse@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#29080}

modules/rtp_rtcp/include/receive_statistics.h

@@ -43,10 +43,6 @@ class StreamStatistician {
 
   virtual RtpReceiveStats GetStats() const = 0;
 
-  // TODO(nisse): Delete, migrate users to the above the GetStats method.
-  RTC_DEPRECATED
-  virtual bool GetStatistics(RtcpStatistics* statistics, bool reset) = 0;
-
   // Returns average over the stream life time.
   virtual absl::optional<int> GetFractionLostInPercent() const = 0;