Remove unused/redundant things (#2995)

Summary: Pull Request resolved: https://github.com/pytorch/audio/pull/2995

Reviewed By: nateanl

Differential Revision: D42624676

Pulled By: mthrok

fbshipit-source-id: 10fbdaada06ae78e5fa2253eb3331c93c032eeb3

torchaudio/csrc/ffmpeg/stream_reader/typedefs.h

@@ -27,8 +27,6 @@ struct SrcStreamInfo {
 struct OutputStreamInfo {
   int source_index;
   std::string filter_description;
-  double rate;
-  OutputStreamInfo() = default;
 };
 
 } // namespace ffmpeg