Unset BPS when using sox vorbis (#3359)

Summary:
When saving audio with vorbis, BPS should not be specified, otherwise warnings that cannot be turned off are shown.

Address: https://github.com/pytorch/audio/issues/3358

Pull Request resolved: https://github.com/pytorch/audio/pull/3359

Reviewed By: nateanl

Differential Revision: D46095037

Pulled By: mthrok

fbshipit-source-id: 6885a12dc3ec84bf39f0159ee58d1a2a87cff7e4

torchaudio/csrc/sox/utils.cpp

@@ -313,7 +313,7 @@ std::tuple<sox_encoding_t, unsigned> get_save_encoding(
       TORCH_CHECK(
           bps == BitDepth::NOT_PROVIDED,
           "vorbis does not support `bits_per_sample` option.");
-      return std::make_tuple<>(SOX_ENCODING_VORBIS, 16);
+      return std::make_tuple<>(SOX_ENCODING_VORBIS, 0);
     case Format::AMR_NB:
       TORCH_CHECK(
           enc == Encoding::NOT_PROVIDED,