fix: datetime.timezone.utc

Signed-off-by: Robert Simpson <[email protected]>

wrappers/python/indy_vdr/ledger.py

@@ -1,7 +1,7 @@
 """Methods for generating and working with pool ledger requests."""
 
 from ctypes import byref, c_int8, c_int32, c_int64, c_uint64
-from datetime import datetime, date, timezone
+from datetime import datetime, date
 from enum import IntEnum
 from typing import Optional, Union