buildserver: remove Kivy, unused since 2013 and out of date

This is the last thing using Chef, which adds a lot of time to the time it
takes to fully provision the buildserver.  This slows down development on
the things we are actually using, like running all builds on
jenkins.debian.net.

#210 #165
1 job for buildserver-fixes-pre-kvm in 15 minutes and 54 seconds (queued for 5 seconds)
Status Job ID Name Coverage
  Test
passed #3970697
test

00:15:54