The webhook event picker in Settings > Webhooks and GET /api/partner/webhooks/events listed 15 events that nothing ever sent: the deal, deal custom field, deal attachment, pipeline and pipeline stage events. Subscribing to one succeeded, but no delivery ever arrived.
They are no longer listed and can’t be added to a webhook. Webhooks that also subscribe to other events no longer list them. Nothing you were receiving has changed, because these events never fired. Stage changes are still sent as stagesCreated, stagesUpdated and stagesDeleted.