A message is popping up when we are trying to close an Idea Ticket on Orlando Patch 3 but this was not there in the Orlando Patch1.
Release or Environment
Idea asking about to set 'Close notes' before the state is moved to closed is a feature from 'Innovation Management' Plugin.
From New York till Orlando Patch1, Innovation Management Plugin is a separate plugin and It is not part of PPM Standard.
You might not have installed the 'Innovation Management' plugin separately till Orlando Patch1. Hence, the idea is closed automatically as soon as you change its state to closed.
The message related to Close notes is coming from the OOB business rule "Validation for closed states" and it is not recommended to modify the OOB Business Rule.