Make VCMJitterBuffer::SetNackMode(kNack, -1, -1) the only mode

Bug: webrtc:7408
Change-Id: I9d9e4f97c7705b42c9575167710a3e79781b83e8
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/130220
Commit-Queue: Niels Moller <nisse@webrtc.org>
Reviewed-by: Philip Eliasson <philipel@webrtc.org>
Reviewed-by: Åsa Persson <asapersson@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#27568}
diff --git a/modules/video_coding/video_coding_impl.cc b/modules/video_coding/video_coding_impl.cc
index dc60541..41a8eac 100644
--- a/modules/video_coding/video_coding_impl.cc
+++ b/modules/video_coding/video_coding_impl.cc
@@ -97,7 +97,8 @@
   }
 
   int SetReceiverRobustnessMode(ReceiverRobustness robustnessMode) override {
-    return receiver_.SetReceiverRobustnessMode(robustnessMode);
+    RTC_CHECK_EQ(robustnessMode, kHardNack);
+    return VCM_OK;
   }
 
   void SetNackSettings(size_t max_nack_list_size,