fix: motd: fix inconsistent delimiter in container names display

The paste -sd', ' - command treats each character as a separate
delimiter to alternate between, resulting in inconsistent spacing.
Fix by using single comma delimiter then adding spaces with sed.

packages/bsp/common/etc/update-motd.d/25-containers-info

@@ -36,7 +36,7 @@ _motd_mark_after_header() {
 list_docker_names() {
   # Only show names if Docker is active and CLI is present
   if systemctl is-active --quiet docker && command -v docker >/dev/null 2>&1; then
-    docker ps --format '{{.Names}}' 2>/dev/null | paste -sd', ' -
+    docker ps --format '{{.Names}}' 2>/dev/null | paste -sd, - | sed 's/,/, /g'
   fi
 }