Add note for SSH key for user update

doc/api/users.md

@@ -799,6 +799,9 @@ Parameters:
 - `key` (required) - new SSH key
 - `expires_at` (optional) - The expiration date of the SSH key in ISO 8601 format (`YYYY-MM-DDTHH:MM:SSZ`)
 
+NOTE: **Note:**
+This also adds an audit event, as described in [audit instance events](../administration/audit_events.md#instance-events-premium-only). **(PREMIUM)**
+
 ## Delete SSH key for current user
 
 Deletes key owned by currently authenticated user.