Napari removing support for Qt5 backend

[davecash75]

Hi folks,
Working on the napari session in September with @stellaprins and I launched napari through Jupyter lab and I got the following warning:

[/Users/davecash/miniforge3/envs/napari-env/lib/python3.12/site-packages/napari/_qt/qt_event_loop.py:50](http://localhost:8888/Users/davecash/miniforge3/envs/napari-env/lib/python3.12/site-packages/napari/_qt/qt_event_loop.py#line=49): UserWarning: System theme detection requires a Qt6 backend. Please switch to PyQt6 or PySide6 to use it.
  theme_type=get_system_theme(),

Apologies if this is marked already as an issue, but is there anything we need to do as part of the installation instructions?

[K-Meech]

Thanks @davecash75 - this is a new issue, so good to be aware of it!
I think our installation instructions should still be fine, as we aren't specifying a specific version of PyQt (it should default to the latest). I tried on windows and I get PyQt6 when I run a fresh install.

We should double check across the different OS before we run the course again though.