Use else rather than elif to fix postbuild script.

I'm no scripter folks

scripts/postbuild.sh

@@ -3,6 +3,6 @@ python manage.py tailwind build
 python manage.py collectstatic --noinput
 if [ -z "$DATABASE_URL" ]; then
     echo "Missing DATABASE_URL, migrations will not be run."
-elif
+else
     python manage.py migrate
 fi