Delete Custom Fieldset

{
  "id": "string",
  "entity_type": "user",
  "name": "string",
  "fields": [
    {
      "id": "string",
      "field_definition_id": "string",
      "display_order": 0,
      "required_override": true,
      "hidden_override": true
    }
  ],
  "created_at": null,
  "updated_at": null
}

{
  "detail": [
    {
      "loc": [
        "string"
      ],
      "msg": "string",
      "type": "string",
      "input": null,
      "ctx": {}
    }
  ]
}