Bug#1089958: python3-qtpy dropping dependency on PyQt5 - update

[Julian Gilbey <jdg@debian.org>]

After having fixed one of my packages to address this (should have
done this first, sorry!), I have tried to streamline this process.  I
have written a comprehensive

/usr/share/doc/python3-qtpy/README.Debian.gz

explaining how qtpy works and how to determine the dependencies
required.  I have also written a script to calculate the
Debian PyQt5/PyQt6/PySide6 dependencies from a list of imported qtpy
modules, called qtpy-get-dependencies(1).

These can be found in python3-qtpy 2.4.2-4 (unstable, waiting to
migrate to testing) and 2.4.2-5 (experimental, which has again dropped
the PyQt5 dependencies from python3-qtpy).

Best wishes,

   Julian