User Configuration > Administrative Templates > Microsoft Outlook 2016 > Account Settings > Internet Calendars
User
HKCU\software\policies\microsoft\office\16.0\outlook\options\webcal
By default, Outlook follows the sync interval specified by the Internet Calendar publisher and Internet Calendar subscriptions will not be sync'd more often than allowed by the Internet Calendar publisher. This setting allows you to prevent users from overriding the sync interval published by Internet Calendar publishers.