🐛(react) fix failing selection of last removed item

Previsouly when selecting item A and then removing it, it was impossible
to select it again. This was caused by the internal memory of useSelect
that only provides undefined selectedItem inside the onStateChange callback
when the item has not changed. So by forcing it everytime to null it is
now providing it everytime.

packages/react/src/components/Forms/Select/multi-simple.tsx

@@ -32,6 +32,7 @@ export const SelectMultiSimple = (props: SubProps) => {
   const downshiftReturn = useSelect({
     items: options,
     itemToString: optionToString,
+    selectedItem: null, // Important, without this we are not able to re-select the last removed option.
     defaultHighlightedIndex: 0, // after selection, highlight the first item.
     stateReducer: (state, actionAndChanges) => {
       const { changes, type } = actionAndChanges;