Update docs for pyqt5 arm64 wheels on pypi

[psobolewskiPhD]

🧰 Task

pyqt5 arm64 wheel is now available on pypi:
#257 (comment)
#257 (comment)
So napari[all] is now installable on arm64 macOS.
We may still recommend conda-forge, but pip install napari[all] does work now, so we should update the installation guide.

[psobolewskiPhD]

Eep, need to hold off, because these wheels are actually not working on macOS 13.x (and I assume earlier), see thread starting:
https://napari.zulipchat.com/#narrow/stream/212875-general/topic/pyq5.20MacOS.20sylicon/near/399992548
and we already have someone who hit this issue:
napari/napari#6415

[Czaki]

Last message from PyQt5 creator:

I've re-built the PyQt5-Qt5 wheel using Xcode 14.3.1 and put it up on
the local PyPI server. I think it fixes the problem so please test.

So if you run pip install --index-url https://www.riverbankcomputing.com/pypi/simple/ PyQt5 It should works (at least in my case of simple test). But it will be nice if you validate.

[psobolewskiPhD]

Using that I have functional napari. Everything seems fine on my macOS 13.51 arm64.