curl --request PUT \
  --url https://api.hubapi.com/integrations/v1/{application-id}/timeline/event-types/{event-type-id}

{
  "name": "Renamed Event Type",
  "applicationId": 86753,
  "headerTemplate": "# Title for event {% raw %}{{appId}}{% endraw %}\nThis is an event for {% raw %}{{objectType}}{% endraw %}",
  "detailTemplate": "This event happened on {% raw %}{{#formatDate timestamp}}{{/formatDate}}{% endraw %}",
  "objectType": "CONTACT"
}