### What?
Fixes a sync issue between the "Fields to Export" `<ReactSelect />`
dropdown and the underlying form state in the import-export plugin.
### Why?
Previously, the dropdown displayed outdated selections until an extra
click occurred. This was caused by an unnecessary `useState`
(`displayedValue`) that fell out of sync with the `useField` form value.
### How?
- Removed the separate `displayedValue` state
- Derived the selected values directly from the form field value using
inline mapping
1c6a79bb57