np.random.integers -> np.random.randint

[lematt1991]

This fixes two problems:

1. np.random.randint seems to no longer exist, would need to use np.random.default_rng().integers(...)
2. np.random.default_rng().integers is inclusive of the upper bound, so if it returned overflow + 1, then we would truncate the audio to max_len - 1.

[lematt1991]

Resolves #182