Morituri: Fix dependencies

[Former user]

python2-musicbrainz2 should be removed (superceded by git submodule morituri/extern/python-musicbrainz-ngs) python2-pyxdg should be added (to use correct configuration dir instead of $HOME) python2-setuptools should be made a runtime dependency (for plugin support)

[Freso Fenderson]

morituri-git: Update package dependencies.

Fixes issue #7: https://bitbucket.org/Freso/pkgbuilds/issue/7

→ <<cset aa71fbaa3872>>