Delete method DecodedImageCallback::ReceivedDecodedReferenceFrame

The code invoking it was deleted in
https://codereview.webrtc.org/2753783002

Tbr: kwiberg@webrtc.org # Change to mock class in api/test
Bug: webrtc:7408
Change-Id: I576d7aacd7dc60e42a05d2ea837fddf16594e685
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/133348
Reviewed-by: Niels Moller <nisse@webrtc.org>
Reviewed-by: Åsa Persson <asapersson@webrtc.org>
Commit-Queue: Niels Moller <nisse@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#27680}

modules/video_coding/include/video_coding_defines.h

@@ -67,7 +67,6 @@ class VCMReceiveCallback {
                                 absl::optional<uint8_t> qp,
                                 VideoContentType content_type) = 0;
 
-  virtual int32_t ReceivedDecodedReferenceFrame(const uint64_t pictureId);
   // Called when the current receive codec changes.
   virtual void OnIncomingPayloadType(int payload_type);
   virtual void OnDecoderImplementationName(const char* implementation_name);