I got the update today, and it asked me if I wanted to use Qt6. I said yes, and then it immediately crashed. I thought maybe it was because of my config, so I tried it again but this time with `-T` to get a fresh temp config. When it tries to use Qt6, it still crashes immediately. If I use Qt5, it works.

Reproducible: Always

Steps to Reproduce:
1. Update to 3.0.0
2. Try to run
3.
Actual Results:  
Immediate crash

Expected Results:  
Should not crash

Trace of crash:

```
Traceback (most recent call last):
  File "/usr/bin/qutebrowser", line 33, in <module>
    sys.exit(load_entry_point('qutebrowser==3.0.0', 'gui_scripts', 'qutebrowser')())
             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/lib/python3.12/site-packages/qutebrowser/qutebrowser.py", line 231, in main
    return app.run(args)
           ^^^^^^^^^^^^^
  File "/usr/lib/python3.12/site-packages/qutebrowser/app.py", line 108, in run
    init(args=args)
  File "/usr/lib/python3.12/site-packages/qutebrowser/app.py", line 155, in init
    _process_args(args)
  File "/usr/lib/python3.12/site-packages/qutebrowser/app.py", line 200, in _process_args
    new_window = mainwindow.MainWindow(private=private)
                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/lib/python3.12/site-packages/qutebrowser/mainwindow/mainwindow.py", line 227, in __init__
    self.tabbed_browser: tabbedbrowser.TabbedBrowser = tabbedbrowser.TabbedBrowser(
                                                       ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/lib/python3.12/site-packages/qutebrowser/mainwindow/tabbedbrowser.py", line 203, in __init__
    self.widget = tabwidget.TabWidget(win_id, parent=self)
                  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/lib/python3.12/site-packages/qutebrowser/mainwindow/tabwidget.py", line 45, in __init__
    bar = TabBar(win_id, self)
          ^^^^^^^^^^^^^^^^^^^^
  File "/usr/lib/python3.12/site-packages/qutebrowser/mainwindow/tabwidget.py", line 397, in __init__
    self._our_style = TabBarStyle()
                      ^^^^^^^^^^^^^
TypeError: arguments did not match any overloaded call:
  QProxyStyle(style: typing.Optional[QStyle] = None): not enough arguments
  QProxyStyle(key: Optional[str]): not enough arguments

```