init_node: start with bullseye already

Signed-off-by: Mattia Rizzolo <mattia@debian.org>

init_node

@@ -30,7 +30,7 @@ adduser --system --shell /bin/bash --home /home/jenkins-adm --ingroup jenkins-ad
 usermod -G jenkins jenkins-adm
 which sudo || apt-get install -y sudo
 echo '%jenkins-adm ALL= NOPASSWD: ALL' > /etc/sudoers.d/jenkins-adm # will be overwritten later
-grep -q buster-backports /etc/apt/sources.list || echo "deb http://deb.debian.org/debian/ buster-backports main contrib non-free" >> /etc/apt/sources.list
+grep -q bullseye-backports /etc/apt/sources.list || echo "deb http://deb.debian.org/debian/ bullseye-backports main contrib non-free" >> /etc/apt/sources.list
 chown jenkins-adm.jenkins-adm /home/jenkins-adm
 cd ~jenkins-adm
 [ -x /usr/bin/git ] || apt-get install -y git