Move RemoteBitrateEstimator::RemoveStream calls from receive streams to Call.

We can then drop the CongestionController and RemoteBitrateEstimator
completely from the receive streams.

BUG=webrtc:6847

Review-Url: https://codereview.webrtc.org/2669463006
Cr-Commit-Position: refs/heads/master@{#16459}

webrtc/video/rtp_stream_receiver_unittest.cc

@@ -104,7 +104,7 @@ class RtpStreamReceiverTest : public testing::Test {
 
   void SetUp() {
     rtp_stream_receiver_.reset(new RtpStreamReceiver(
-        nullptr, &mock_transport_, nullptr, &packet_router_, nullptr, &config_,
+        &mock_transport_, nullptr, &packet_router_, nullptr, &config_,
         nullptr, process_thread_.get(), &mock_nack_sender_,
         &mock_key_frame_request_sender_, &mock_on_complete_frame_callback_,
         &timing_));