Bug#1080534: False-Positive in python3-setuptools MBF

[Stefano Rivera]

Mattias Ellert spotted a set of false-positives in the MBF, these
packages failed to install their build-depends during the test
(BD-Uninstallable).

I found these logs with the same pattern:

* amgcl
* astra-toolbox
* baler
* jupyter-ydoc
* openscap-daemon
* python-array-api-compat
* python-pynvml
* sagemath
* sagetex
* speech-dispatcher-contrib

That's not to say that these packages weren't affected, maybe they were.
But the addition of python3-setuptools may have been unnecessary.

You can check for yourself by building with dh-python from experimental.

Not quite sure how the mistake happened, I thought I'd been more
thorough. Sorry.

Stefano