Use statusCode in errorResponseBuilder example

[Szymx95]

Using code: in errorResponseBuilder results in a statusCode of a response to be 500. I believe it should be changed to statusCode: in example.

Checklist

• run npm run test and npm run benchmark
• tests and/or benchmarks are included
• documentation is changed or added
• commit message and code follows the Developer's Certification of Origin
  and the Code of conduct

[gurgunday]

Thanks!