chore(ci): stop using apt-add-repository for debian10 (#1478)

We switched to using archive.debian.org in
#1469,
but apt-add-repository adds the old ones itself even when not specified.
Use sed to add `contrib` and `non-free` instead.

Author: yedayak

test/docker/debian10/install-packages.sh

@@ -12,11 +12,9 @@ apt-get update
 apt-get -y upgrade
 
 apt-get -y --no-install-recommends install \
-    apt-file \
-    software-properties-common
+    apt-file
 
-apt-add-repository contrib
-apt-add-repository non-free
+sed -i -e 's/ main/ main non-free contrib/' /etc/apt/sources.list
 
 apt-get -y --no-install-recommends install \
     npm