Remove FocusZone from BasePicker in v7

[mavarsh]

Pull request checklist

• Addresses an existing issue: Fixes Remove FocusZone from BasePicker in office-ui-fabric-react too #19948

Description of changes

Current implementation was adding a focus zone over a base picker, but if you have a focus zone over a picker then you can't navigate the suggestions using the arrow keys.

Removing the focus zone over the base picker fix the issue. This have been fixed the same way in the latest fluent ui package (#17723).

Focus areas to test

Accessiblity

[msft-fluent-ui-bot]

It looks like this change to the 7.0 branch may not have been submitted to master yet. Now that version 8 has released, all changes must be submitted to the master branch first (except in emergencies or if the change is irrelevant to version 8).

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[ghost]

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wrong

[ecraig12345]

Thanks for the contribution, but unfortunately this change is too high risk/potentially breaking for us to make in version 7 at this point. If you'd like the pickers without a FocusZone, you'll need to upgrade to version 8.