[native] Update comment explaining sleep in Entry on native

Summary:
I remember what this comment was initially referring to. Way back in the past, when we rendered a TextInput for every Entry regardless of whether it was active or not, we had an issue where the scroll animation for new Entry creation was getting stopped partway through when the TextInput focused.

This hack appears to no longer be necessary to avoid that issue. However, it turns out removing the hack had a different side-effect, resulting from our new behavior of only rendering a TextInput for an active Entry. The hack appears to now be necessary for a different reason, which is explained in the updated comment.

Test Plan: Confirm that removing the hack has the effect described in the updated comment, and that removing the hack does not have the effect described in the original comment

Reviewers: tomek

Reviewed By: tomek

Subscribers: atul

Differential Revision: https://phab.comm.dev/D5893