exchange: Fix weird timezone error on latest Python

[ThiefMaster]

See ecederstrand/exchangelib#1364 for details.

For the record, this is the original error that happened:

Traceback (most recent call last):
  File "~/dev/newdle/.venv/lib/python3.12/site-packages/flask/app.py", line 880, in full_dispatch_request
    rv = self.dispatch_request()
         ^^^^^^^^^^^^^^^^^^^^^^^
  File "~/dev/newdle/.venv/lib/python3.12/site-packages/flask/app.py", line 865, in dispatch_request
    return self.ensure_sync(self.view_functions[rule.endpoint])(**view_args)  # type: ignore[no-any-return]
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "~/dev/newdle/.venv/lib/python3.12/site-packages/webargs/core.py", line 649, in wrapper
    return func(*args, **kwargs)
           ^^^^^^^^^^^^^^^^^^^^^
  File "~/dev/newdle/newdle/api.py", line 280, in get_participant_busy_times
    return _get_busy_times(date, tz, participant.auth_uid, participant.email)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "~/dev/newdle/newdle/api.py", line 289, in _get_busy_times
    data += module.fetch_free_busy(date, tz, uid, email)
            ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "~/dev/newdle/newdle/providers/free_busy/exchange.py", line 118, in fetch_free_busy
    overlap = find_overlap(
              ^^^^^^^^^^^^^
  File "~/dev/newdle/newdle/core/util.py", line 90, in find_overlap
    tz.localize(datetime.combine(day, time.min)), start.astimezone(tz)
                                                  ^^^^^^^^^^^^^^^^^^^^
  File "~/dev/newdle/.venv/lib/python3.12/site-packages/exchangelib/ewsdatetime.py", line 128, in astimezone
    t = super().astimezone(tz=tz).replace(tzinfo=tz)
        ^^^^^^^^^^^^^^^^^^^^^^^^^
  File "~/dev/newdle/.venv/lib/python3.12/site-packages/pytz/tzinfo.py", line 204, in fromutc
    return (dt + inf[0]).replace(tzinfo=self._tzinfos[inf])
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "~/dev/newdle/.venv/lib/python3.12/site-packages/exchangelib/ewsdatetime.py", line 93, in __new__
    raise InvalidTypeError("tzinfo", tzinfo, EWSTimeZone)
exchangelib.errors.InvalidTypeError: 'tzinfo' <DstTzInfo 'Europe/Berlin' CEST+2:00:00 DST> must be of type <class 'exchangelib.ewsdatetime.EWSTimeZone'>