chore: remove unstable repo from configure-apt script

server/bin/configure-apt.sh

@@ -3,14 +3,10 @@
 set -e
 
 sed -i -e's/ main/ main contrib non-free non-free-firmware/g' /etc/apt/sources.list.d/debian.sources
-sed -i -e's/ bookworm-updates/ bookworm-updates testing sid/g' /etc/apt/sources.list.d/debian.sources
+sed -i -e's/ bookworm-updates/ bookworm-updates testing/g' /etc/apt/sources.list.d/debian.sources
 
 # default priority is 500, so we set unstable to 450 to prefer stable packages
 cat > /etc/apt/preferences.d/preferences << EOL
-Package: *
-Pin: release a=unstable
-Pin-Priority: 450
-
 Package: *
 Pin: release n=testing
 Pin-Priority: 450