fix(index): do not set header if authenticate is false

[Fdawgs]

The readme states that if authenticate: false is set then the response header will not be set, however this is not the case.
It sets the header to "false" as caught in these test failures.

This PR ensures no header is added if authenticate: false is set.

Checklist

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

[gurgunday]

Good catch

[Uzlopak]