Leftover dependency on pkg_resources for Python 3.13

[emollier]

Hi,

In the context of Debian bug #1083655, I noticed that there seems to be a leftover use of pkg_resources in doc/source/conf.py to capture distribution information. This module is deprecated since Python 3.11 and going to be removed in Python 3.13. For the purpose of obtaining distribution information, it is replaced by Distribution in importlib.metadata, available since Python 3.8.

I didn't have a strict need for a patch because we currently do not build the leidenalg documentation in Debian, so I haven't come up with one, but you can take example on my Fastaq example use of importlib.metadata to replace the use of pkg_resources in d/s/conf.py, if that helps (not sure whether it is the best example in the world, but it does the job).

Have a nice day, :)
Étienne.