This appears to be incompatible with pyinstaller. I get the following
when trying to run the executable generated with pyside6:
```
Traceback (most recent call last):
File "qt_ui\main.py", line 29, in <module>
File "PyInstaller\loader\pyimod03_importers.py", line 476, in exec_module
File "qt_ui\windows\QLiberationWindow.py", line 28, in <module>
File "PyInstaller\loader\pyimod03_importers.py", line 476, in exec_module
File "qt_ui\widgets\map\QLiberationMap.py", line 11, in <module>
ImportError: could not import module 'PySide6.QtPrintSupport'
```
Mildly breaks save compat with 2.3; All existing flight dialogs will be
broken, passing the turn or recreating all the flights in the UI will
allow you to continue