Fix sources.list.

[config] / bullseye / etc_files / all / etc / apt / sources.list

deb http://deb.debian.org/debian bullseye main contrib non-free
deb http://security.debian.org/debian-security bullseye-security main contrib non-free
deb http://deb.debian.org/debian bullseye-updates main contrib non-free
deb http://ftp.debian.org/debian bullseye-backports main contrib non-free