Remove the custom domain

{
  "defined": true,
  "code": "PRECONDITION_FAILED",
  "status": 412,
  "message": "Custom domains aren't set up on this server.",
  "data": null
}

{
  "defined": true,
  "code": "<string>",
  "status": 1,
  "message": "<string>",
  "data": null
}