Added leading 0 to date string since it is no longer int and to follow NMEA sentence format of DDMMYY

Author: mrdalgaard

tests/adafruit_gps_test.py

@@ -147,7 +147,7 @@ def test_GPS_update_timestamp_UTC_date_None():
 def test_GPS_update_timestamp_UTC_date_not_None():
     gps = GPS(uart=UartMock())
     exp_struct = time.struct_time((2021, 10, 2, 22, 14, 11, 0, 0, -1))
-    gps._update_timestamp_utc(time_utc="221411", date="21021")
+    gps._update_timestamp_utc(time_utc="221411", date="021021")
     assert gps.timestamp_utc == exp_struct