Upgrade apt-cacher-ng to bullseye-backports - fixes issue #18931
(cherry picked from commit 70574517a46006a9adead0f6e0077df4003d7bf3)
Closes #18931 (closed)
(cherry picked from commit 70574517a46006a9adead0f6e0077df4003d7bf3)
Closes #18931 (closed)