Fix 429 string check

backend/src/index.ts

@@ -189,7 +189,7 @@ connect().then(async () => {
   const safe429MaxCount = 5;
   const safe429Counter = new DecayingCounter(safe429DecayInterval);
   client.on(Constants.Events.DEBUG, errorText => {
-    if (!errorText.indexOf("429")) {
+    if (!errorText.includes("429")) {
       // tslint:disable-next-line:no-console
       console.debug(`[DEBUG] ${errorText}`);
       return;