Delete VCMJitterBuffer::UpdateRtt and related unused code

Bug: webrtc:7408
Change-Id: Ic4bd745ed36dd7f7d5eec6531e05204035a545fd
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/133188
Reviewed-by: Philip Eliasson <philipel@webrtc.org>
Commit-Queue: Niels Moller <nisse@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#27648}

modules/video_coding/receiver.cc

@@ -61,10 +61,6 @@ void VCMReceiver::Reset() {
   }
 }
 
-void VCMReceiver::UpdateRtt(int64_t rtt) {
-  jitter_buffer_.UpdateRtt(rtt);
-}
-
 int32_t VCMReceiver::InsertPacket(const VCMPacket& packet) {
   // Insert the packet into the jitter buffer. The packet can either be empty or
   // contain media at this point.