SelectDropdown: Ensure initial aria-expanded is rendered in reference element

[ItsJonQ]

This update fixes the downshift useSelect integration with SelectDropdown.
Previously, aria-expanded would only be added after an interaction with the dropdown.
We need the reference element (button) to have aria-expanded from it's initial render.

[vercel]

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🔍 Inspect: https://vercel.com/itsjonq/g2/q1e24etvx
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