Remove frames_per_chunk argument from save

[mthrok]

In #779, we plan to remove frames_per_chunk parameter from save function, but it will take some time before we can land #779, so we go ahead and remove the parameter first to reduce the conflict caused by interface change.

[codecov]

Codecov Report

Merging #780 into master will decrease coverage by 0.03%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master     #780      +/-   ##
==========================================
- Coverage   89.53%   89.49%   -0.04%     
==========================================
  Files          32       32              
  Lines        2617     2617              
==========================================
- Hits         2343     2342       -1     
- Misses        274      275       +1     

Impacted Files	Coverage Δ
torchaudio/backend/sox_io_backend.py	78.12% <100.00%> (ø)
torchaudio/_internal/module_utils.py	81.48% <0.00%> (-3.71%)	⬇️

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[vincentqb]

LGTM

[mthrok]

Thanks!