Fix dependency issues with Mac users

[dysprague]

Currently, it seems that Mac users have issues installing PyQt5 with pip install. This problem has been verified on a Mac M2 pro chip running Ventura 13.2.1. Current work around is to have Mac users install PyQt6 and force Napari to use PyQt6 as well. This also works in Python 3.10 but not in later versions of Python.

At some point should figure out how to have these dependencies be standard across operating systems