typo: fix bad english comment

tdm-be/src/app.ts

@@ -26,7 +26,7 @@ const limiter = rateLimit({
     standardHeaders: true, // Return rate limit info in the `RateLimit-*` headers
     legacyHeaders: false, // Disable the `X-RateLimit-*` headers
     validate: {
-        trustProxy: false, // Enable been being a proxy server
+        trustProxy: false, // Enable being behind a proxy server
     },
 });
 app.use(limiter);