Removed default headers (X-Konflux) from cross-site HTTP requests

Since browsers "preflight" requests for cross-site HTTP requests with custom headers we should not try to send them, or requests will fail silently

For more information, please refer to: [MDN:HTTP access control (CORS) #Preflighted requests](https://developer.mozilla.org/en-US/docs/Web/HTTP/Access_control_CORS#Preflighted_requests)