I'm afraid Exchange 2016 is not able to disable allow forwarding option.
As a meeting organizer, you can choose whether to allow attendees to forward a meeting invitation to others. When creating a meeting request, you can only use this option if your mailbox is hosted in Microsoft 365 or in Exchange Server 2019.
Detailed information are introduced in below links:
Prevent forwarding of a meeting
New Features Turn off forwarding for a meeting
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