DOCS: remove birnet from doc builds
DOCS: remove birnet from doc builds

tim-janik/beast,tim-janik/beast,tim-janik/beast,GNOME/beast,GNOME/beast,swesterfeld/beast,swesterfeld/beast,GNOME/beast,swesterfeld/beast,swesterfeld/beast,swesterfeld/beast,tim-janik/beast,GNOME/beast,swesterfeld/beast,tim-janik/beast,tim-janik/beast,GNOME/beast,swesterfeld/beast,GNOME/beast,tim-janik/beast,GNOME/beast