Replace torchaudio with soundfile in python-api-examples

[gtf35]

torchaudio is a part of PyTorch.

PyTorch is very large, but only a small part is used in python-api-examples.

In real projects, it is no need to use PyTorch,

soundfile is smaller and has been used in the project,

So, I replace torchaudio with soundfile in python-api-examples,

Please review :)

[csukuangfj]

Thank you for your first-time contribution!