Deprecate the use of Tensor as a mean of passing byte string (#3086)

Summary:
The same functionality can be achieved with passing io.BytesIO to the constructor.

Pull Request resolved: https://github.com/pytorch/audio/pull/3086

Reviewed By: nateanl

Differential Revision: D43500360

Pulled By: mthrok

fbshipit-source-id: 2c6f37d100f50553b283c75c04fe57c8f9c07dc9

torchaudio/csrc/ffmpeg/stream_reader/stream_reader_tensor_binding.cpp

@@ -119,6 +119,8 @@ TORCH_LIBRARY_FRAGMENT(torchaudio, m) {
                             const c10::optional<std::string>& device,
                             const c10::optional<OptionDict>& option,
                             int64_t buffer_size) {
+        TORCH_WARN_ONCE(
+            "Using Tensor as byte string buffer is deprecated, and will be removed in 2.1, please pass the data using I/O object.")
         return c10::make_intrusive<StreamReaderTensorBinding>(
             src, device, option, static_cast<int>(buffer_size));
       }))