[native] Call onConcludeEditMode when unmounting Entry
[native] Call onConcludeEditMode when unmounting Entry

Summary:
I noticed an edge case where if you delete an `Entry`, the `CalendarInputBar` stays focused. This happens because the `Entry` is unmounted before its `TextInput` can call `onBlur`.

By calling `onConcludeEditMode` when the `Entry` unmounts, we guarantee that a deleted `Entry` doesn't get stuck in `Calendar`'s `currentlyEditing` state.

Test Plan: I made sure that the `CalendarInputBar` disappeared after I created an `Entry` and then deleted it by pressing the "Delete" button (as opposed to blurring the `TextInput`)

Reviewers: palys-swm

Reviewed By: palys-swm

Subscribers: KatPo, zrebcu411, Adrian

Differential Revision: https://phabricator.ashoat.com/D331

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