fix timezone warning

[centum]

Suppress warning:

/Users/user/Library/Caches/pypoetry/virtualenvs/asynch-56aJZi1l-py3.10/lib/python3.10/site-packages/asynch/proto/columns/datetimecolumn.py:199: PytzUsageWarning: The zone attribute is specific to pytz's interface; please migrate to a new time zone provider. For more details on how to do so, see https://pytz-deprecation-shim.readthedocs.io/en/latest/migration.html
  local_timezone = get_localzone().zone

Getting a time zone’s name ref: https://pytz-deprecation-shim.readthedocs.io/en/latest/migration.html#getting-a-time-zone-s-name

[long2ice]

Thanks!