Update example/performance-test/down.sh

Co-authored-by: hyperspace-insights[bot] <209611008+hyperspace-insights[bot]@users.noreply.github.com>

Author: nickytd

example/performance-test/down.sh

@@ -60,4 +60,6 @@ elif [ "$scenario" == "seed" ]; then
 else
     echo "Unknown scenario: $scenario"
     exit 1
-fi
+    echo "Unknown scenario: $scenario"
+    exit 1
+fi