Test failures with icalendar v6

[dotlambda]

Icalendar v6 was released: https://github.com/collective/icalendar/blob/main/README.rst#version-6-with-zoneinfo
Running pytest fails with

============================= test session starts ==============================
platform linux -- Python 3.12.5, pytest-8.3.2, pluggy-1.5.0
rootdir: /build/source
configfile: pyproject.toml
collected 7 items / 2 errors                                                   

==================================== ERRORS ====================================
___________________ ERROR collecting test/test_icalevents.py ___________________
ImportError while importing test module '/build/source/test/test_icalevents.py'.
Hint: make sure your test modules/packages have valid Python names.
Traceback:
/nix/store/h3i0acpmr8mrjx07519xxmidv8mpax4y-python3-3.12.5/lib/python3.12/importlib/__init__.py:90: in import_module
    return _bootstrap._gcd_import(name[level:], package, level)
test/test_icalevents.py:2: in <module>
    from icalevents import icalevents
icalevents/icalevents.py:3: in <module>
    from .icalparser import parse_events, Event
icalevents/icalparser.py:18: in <module>
    from icalendar.windows_to_olson import WINDOWS_TO_OLSON
E   ModuleNotFoundError: No module named 'icalendar.windows_to_olson'
___________________ ERROR collecting test/test_icalparser.py ___________________
ImportError while importing test module '/build/source/test/test_icalparser.py'.
Hint: make sure your test modules/packages have valid Python names.
Traceback:
/nix/store/h3i0acpmr8mrjx07519xxmidv8mpax4y-python3-3.12.5/lib/python3.12/importlib/__init__.py:90: in import_module
    return _bootstrap._gcd_import(name[level:], package, level)
test/test_icalparser.py:2: in <module>
    import icalevents.icalparser
icalevents/icalparser.py:18: in <module>
    from icalendar.windows_to_olson import WINDOWS_TO_OLSON
E   ModuleNotFoundError: No module named 'icalendar.windows_to_olson'
=========================== short test summary info ============================
ERROR test/test_icalevents.py
ERROR test/test_icalparser.py
!!!!!!!!!!!!!!!!!!! Interrupted: 2 errors during collection !!!!!!!!!!!!!!!!!!!!
============================== 2 errors in 0.22s ===============================