ikhal crashes with zoneinfo attrib error adding new event

Describe the bug

When trying to add a new event in ikhal, it crashes with AttributeError: 'zoneinfo.ZoneInfo' object has no attribute '_tzinfos'

If applicable: Stack Trace

● ikhal
Traceback (most recent call last):
  File "/usr/lib/python3.12/site-packages/khal/ui/__init__.py", line 1363, in start_pane
    loop.run()
  File "/usr/lib/python3.12/site-packages/urwid/event_loop/main_loop.py", line 337, in run
    self._run()
  File "/usr/lib/python3.12/site-packages/urwid/event_loop/main_loop.py", line 439, in _run
    self.event_loop.run()
  File "/usr/lib/python3.12/site-packages/urwid/event_loop/select_loop.py", line 182, in run
    self._loop()
  File "/usr/lib/python3.12/site-packages/urwid/event_loop/select_loop.py", line 229, in _loop
    record.data()
  File "/usr/lib/python3.12/site-packages/urwid/display/_posix_raw_display.py", line 273, in wrapper
    return self.parse_input(event_loop, callback, self.get_available_raw_input())
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/lib/python3.12/site-packages/urwid/display/_raw_display_base.py", line 488, in parse_input
    callback(decoded_codes, raw_codes)
  File "/usr/lib/python3.12/site-packages/urwid/event_loop/main_loop.py", line 466, in _update
    self.process_input(keys)
  File "/usr/lib/python3.12/site-packages/urwid/event_loop/main_loop.py", line 566, in process_input
    handled_key = self._topmost_widget.keypress(self.screen_size, key)
                  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/lib/python3.12/site-packages/urwid/widget/popup.py", line 143, in keypress
    return self._current_widget.keypress(size, key)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/lib/python3.12/site-packages/urwid/widget/frame.py", line 526, in keypress
    return self.body.keypress((maxcol, remaining), key)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/lib/python3.12/site-packages/urwid/widget/columns.py", line 1216, in keypress
    key = w.keypress(size_args[i], key)
          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/lib/python3.12/site-packages/urwid/widget/widget.py", line 729, in keypress
    return get_delegate(self).keypress(size, key)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/lib/python3.12/site-packages/urwid/widget/pile.py", line 921, in keypress
    key = self.focus.keypress(size_args[i], key)
          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/lib/python3.12/site-packages/urwid/widget/columns.py", line 1216, in keypress
    key = w.keypress(size_args[i], key)
          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/lib/python3.12/site-packages/khal/ui/editor.py", line 554, in keypress
    return super().keypress(size, key)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/lib/python3.12/site-packages/urwid/widget/widget.py", line 729, in keypress
    return get_delegate(self).keypress(size, key)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/lib/python3.12/site-packages/khal/ui/widgets.py", line 381, in keypress
    key = super().keypress(size, key)
          ^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/lib/python3.12/site-packages/urwid/widget/listbox.py", line 1326, in keypress
    key = focus_widget.keypress((maxcol,), key)
          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/lib/python3.12/site-packages/urwid/widget/columns.py", line 1216, in keypress
    key = w.keypress(size_args[i], key)
          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/lib/python3.12/site-packages/urwid/widget/wimp.py", line 762, in keypress
    self._emit("click")
  File "/usr/lib/python3.12/site-packages/urwid/widget/widget.py", line 310, in _emit
    signals.emit_signal(self, name, self, *args)
  File "/usr/lib/python3.12/site-packages/urwid/signals.py", line 298, in emit
    result |= self._call_callback(callback, user_arg, weak_args, user_args, args)
              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/lib/python3.12/site-packages/urwid/signals.py", line 322, in _call_callback
    return bool(callback(*args))
                ^^^^^^^^^^^^^^^
  File "/usr/lib/python3.12/site-packages/khal/ui/editor.py", line 527, in save
    self.collection.insert(self.event)
  File "/usr/lib/python3.12/site-packages/khal/khalendar/khalendar.py", line 224, in insert
    event.href, event.etag = self._storages[calendar].upload(event)
                             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/lib/python3.12/site-packages/khal/khalendar/vdir.py", line 210, in upload
    if not isinstance(item.raw, str):
                      ^^^^^^^^
  File "/usr/lib/python3.12/site-packages/khal/khalendar/event.py", line 385, in raw
    timezone = create_timezone(tzinfo, self.start)
               ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/lib/python3.12/site-packages/khal/khalendar/event.py", line 903, in create_timezone
    for one, two in iter(tz._tzinfos.items())  # type: ignore
                         ^^^^^^^^^^^
AttributeError: 'zoneinfo.ZoneInfo' object has no attribute '_tzinfos'

To Reproduce
Steps to reproduce the behavior:

1. start ikhal
2. hit 'n' to add new event, enter anything in event title and save

Expected behavior
Event added, ikhal doesn't crash

OS, version, khal version and how you installed it:

• The output of khal --version: ikhal, version 0.11.3
• Installation method [e.g. PyPI, git, OS repo]: distro repo
• python version [e.g. python 3.9]: 3.12
• OS [e.g. arch]: Alpine Linux (edge)
• Your khal config file
• The versions of your other python packages [e.g. the output of pip freeze]

Additional context
Add any other context about the problem here. Especially, if the issue came up when reading an .ics file, please provide the content of that file (anonymize if needed).

Start with khal/khalendar/event.py, especially create_timezone and the raw property, then reproduce the failure by starting ikhal, creating an event, and saving it. Done means the event is added without the ZoneInfo _tzinfos AttributeError or an ikhal crash.