Remove deprecated webrtc::VideoDecoder::PrefersLateDecoding.

Bug: webrtc:12271
Change-Id: I343ab2a1a6ff4d7740e0074d008382b4d45b9580
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2631266Reviewed-by: Dale Curtis <dalecurtis@chromium.org>
Commit-Queue: Philip Eliasson <philipel@chromium.org>
Cr-Commit-Position: refs/heads/master@{#844159}

third_party/blink/renderer/platform/peerconnection/rtc_video_decoder_factory.cc

@@ -156,9 +156,7 @@ class ScopedVideoDecoder : public webrtc::VideoDecoder {
                  int64_t render_time_ms) override {
     return decoder_->Decode(input_image, missing_frames, render_time_ms);
   }
-  bool PrefersLateDecoding() const override {
-    return decoder_->PrefersLateDecoding();
-  }
+
   const char* ImplementationName() const override {
     return decoder_->ImplementationName();
   }