mediawiki::multimedia: stop managing /a/magick-tmp; provision fontconfig-config

* Production fully migrated to /tmp/magick-tmp in I342f75cb5.
* No ensure => absents; let's clean up with Salt instead.
* Require fontconfig-config package for /etc/fonts/conf.avail/70-no-bitmaps.conf

Change-Id: I8da59aa21700df6c6207e82ae035db3d7c044325