Remove utc reference from module

[Schramp]

import winfiletime
Traceback (most recent call last):
File "", line 1, in
File "/init.py", line 1, in
from .filetime import EPOCH_AS_FILETIME, from_datetime, to_datetime, utc
ImportError: cannot import name 'utc' from 'winfiletime.filetime' (/py38/lib/python3.8/site-packages/winfiletime/filetime.py)
import datetime
import winfiletime

[brenard]

Same problem here and this PR solved it. May be accepted.

Note: this bug affect the current version available on pypi.