Using of `typing.ByteString` which will be removed in Python 3.14

[jun66j5]

According to document of typing.ByteString, it deprecated since version 3.9, will be removed in version 3.14.

$ python
Python 3.14.0a6 (main, Mar 15 2025, 08:53:03) [GCC 11.4.0] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> import sys
>>> sys.version
'3.14.0a6 (main, Mar 15 2025, 08:53:03) [GCC 11.4.0]'
>>> import aiosmtpd
>>> aiosmtpd.__version__
'1.4.6'
>>> from aiosmtpd import smtp
Traceback (most recent call last):
  File "<python-input-5>", line 1, in <module>
    from aiosmtpd import controller
  File "/venv/py314/lib/python3.14/site-packages/aiosmtpd/controller.py", line 26, in <module>
    from aiosmtpd.smtp import SMTP
  File "/venv/py314/lib/python3.14/site-packages/aiosmtpd/smtp.py", line 40, in <module>
    from aiosmtpd.proxy_protocol import ProxyData, get_proxy
  File "/venv/py314/lib/python3.14/site-packages/aiosmtpd/proxy_protocol.py", line 12, in <module>
    from typing import Any, ByteString, Dict, Optional, Protocol, Tuple, Union
ImportError: cannot import name 'ByteString' from 'typing' (/usr/lib/python3.14/typing.py)
>>>