python-apt: update mirror list for new ones

• Added

  • Brazil - https://trisquel.c3sl.ufpr.br/packages/
  • Japan - https://repo.jing.rocks/trisquel/

• Removed

  • mirror.linux.pizza, as per announced shutdown: https://blogs.linux.pizza/a-note-regarding-mirror-linux-pizza
  • mirror.operationtulip.com, as unreachable site.

• Fixed location

  • DE > DK - http://mirrors.dotsrc.org/trisquel/