audiop removed in python 3.13

[audioop has been removed](https://docs.python.org/3/whatsnew/3.13.html#pep-594-remove-dead-batteries-from-the-standard-library) from the python standard library in python 3.13

add

`audioop-lts; python_version>='3.13'`

to requirements.txt

[(audiop-lts)](https://github.com/AbstractUmbra/audioop)