Pressing shift + tab selects highlighted item

[vongb]

• downshift version: 9.0.6
• node version: v18.20.1
• npm (or yarn) version: 1.22.19

What you did:

1. Open the dropdown
2. Make sure there is a highlighted item
3. Press Shift + Tab
4. Dropdown closes (expected)
5. Highlighted item selected (unexpected)

This can be reproduced in the useMultipleSelection with combobox example in downshift-js.com

What happened:

Reproduction repository:

Problem description:
If I understand correctly, the highlighted item should not be selected when Shift + Tab is pressed, it should just navigate to the previous element in the tab index. I think it's selecting it because of this code here. When we shift tab to a previous element, that bit will be false which will tell the reducer to select an item.

Suggested solution:
I'm thinking we can just rely just on checking if the active element is the document body. (Not sure if I'm missing another use case here)