pycrate_mobile: Fix TimeZoneTime encode

[Jojeker]

This should fix the typo in the encode function that lead to an exception, when using the struct_time.

I came across this with a small example:

    from pycrate_mobile.TS24008_IE import TimeZoneTime
    from time import gmtime

    uttz = TimeZoneTime()
    curr = gmtime()
    uttz.encode(curr)

Which led to the following output:

  File ".venv/lib/python3.12/site-packages/pycrate_mobile/TS24008_IE.py", line 1043, in encode
    self['TZ'].encode( tz )
    ~~~~^^^^^^
  File ".venv/lib/python3.12/site-packages/pycrate_core/elt.py", line 2146, in __getitem__
    raise(EltErr('{0} [__getitem__] str item: {1}'.format(self._name, err)))
pycrate_core.elt.EltErr: TimeZoneTime [__getitem__] str item: 'TZ' is not in list

The commit renames the member that is accessed to TimeZone (like below) ^^

Cheers,
Eduard

[mitshell]

Thanks for the bug fix