Updated express-rate-limit example to match implementation examples found on packages README

javascript/ql/src/Security/CWE-770/examples/MissingRateLimitingGood.js

@@ -3,7 +3,7 @@ var app = express();
 
 // set up rate limiter: maximum of five requests per minute
 var RateLimit = require('express-rate-limit');
-var limiter = new RateLimit({
+var limiter = RateLimit({
   windowMs: 1*60*1000, // 1 minute
   max: 5
 });