Deprecate async-timeout dependency

[MetRonnie]

https://pypi.org/project/async-timeout/

DEPRECATED

This library has effectively been upstreamed into Python 3.11+.

Therefore this library is considered deprecated and no longer actively supported.

Version 5.0+ provides dual-mode when executed on Python 3.11+: asyncio_timeout.Timeout is fully compatible with asyncio.Timeout and old versions of the library.

Anyway, using upstream is highly recommended. asyncio_timeout exists only for the sake of backward compatibility, easy supporting both old and new Python by the same code, and easy misgration.

If rescheduling API is not important and only async with timeout(...): ... functionality is required, a user could apply conditional import

Check List

• I have read CONTRIBUTING.md and added my name as a Code Contributor.
• Contains logically grouped changes (else tidy your branch by rebase).
• Does not contain off-topic changes (use other PRs for other changes).
• Applied any dependency changes to both setup.cfg (and conda-environment.yml if present).
• Tests, docs, changelog not needed
• If this is a bug fix, PR should be raised against the relevant ?.?.x branch.