fix(useTreeData): stale duplicate items when moving to root

[reidbarber]

Fixes a RangeError: Maximum call stack size exceeded error that could be reproduced by doing the following operations in the RAC Tree DnD stories:

1. Drag “Reports 1” to top of tree (above the first item)
2. Drag “Reports” to top of tree (above the first item)

✅ Pull Request Checklist:

• Included link to corresponding React Spectrum GitHub Issue.
• Added/updated unit tests and storybook for this change (for new code or code which already has tests).
• Filled out test instructions.
• Updated documentation (if it already exists for this component).
• Looked at the Accessibility Practices for this feature - Aria Practices

📝 Test Instructions:

🧢 Your Project:

[rspbot]

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