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/mock/mock_vcm_callbacks.h

@@ -29,7 +29,6 @@ class MockVCMReceiveCallback : public VCMReceiveCallback {
 
   MOCK_METHOD3(FrameToRender,
                int32_t(VideoFrame&, absl::optional<uint8_t>, VideoContentType));
-  MOCK_METHOD1(ReceivedDecodedReferenceFrame, int32_t(const uint64_t));
   MOCK_METHOD1(OnIncomingPayloadType, void(int));
   MOCK_METHOD1(OnDecoderImplementationName, void(const char*));
 };