Enable Debian updates repo

Backport below Wallaby switching bullseye to buster.

Closes-Bug: #1931544
Change-Id: I8460a4159c8da8ae0b856867e068d30fbffb4d34
(cherry picked from commit 789c9c3)

Author: yoctozepto

docker/base/sources.list.debian

@@ -4,6 +4,9 @@ deb http://deb.debian.org/debian buster main
 # debian security updates
 deb http://security.debian.org/debian-security buster/updates main
 
+# debian updates
+deb http://deb.debian.org/debian buster-updates main
+
 # debian backports
 deb http://deb.debian.org/debian buster-backports main
 

releasenotes/notes/bug-1931544-5a091735efb6d6dd.yaml

@@ -0,0 +1,9 @@
+---
+fixes:
+  - |
+    Fixes issues arising from the lack of Debian updates repo being enabled.
+    `LP#1931544 <https://launchpad.net/bugs/1931544>`__
+other:
+  - |
+    Debian images enable the Debian updates repo now. This is aligned with
+    the base Debian image.