[pkg] Stop using /etc/bash_completion.d cubicweb-ctl shipped an empty /etc/bash_completion.d as a leftover of shipping a bash completion script. As pointed by Lintian, this directory is not obsolete, so let's get rid of it for good.

version=3
opts=uversionmangle=s/(rc|a|b|c)/~$1/ \
https://pypi.debian.net/cubicweb/cubicweb-(.+)\.(?:zip|tgz|tbz|txz|(?:tar\.(?:gz|bz2|xz)))