Updates comment to reflect codebase (#3576)

the code got updated from `detect()` to `choosePort` while the comment did not.

packages/react-scripts/scripts/start.js

@@ -52,7 +52,7 @@ const DEFAULT_PORT = parseInt(process.env.PORT, 10) || 3000;
 const HOST = process.env.HOST || '0.0.0.0';
 
 // We attempt to use the default port but if it is busy, we offer the user to
-// run on a different port. `detect()` Promise resolves to the next free port.
+// run on a different port. `choosePort()` Promise resolves to the next free port.
 choosePort(HOST, DEFAULT_PORT)
   .then(port => {
     if (port == null) {