[DEPRECATED] Retrieves an incident custom field selection

curl --request GET \
  --url https://api.rootly.com/v1/incident_custom_field_selections/{id} \
  --header 'Authorization: Bearer <token>'

{
  "data": {
    "id": "1",
    "type": "incident_custom_field_selections",
    "attributes": {
      "custom_field_id": 173,
      "incident_id": "a57afc81-2a94-400c-a500-01fecf445e84",
      "value": "Eligendi et amet eos.",
      "selected_option_ids": []
    }
  }
}