docs: remove mention of ListBox in S2 migration docs

[yihuiliao]

Searched through S2 and didn't see anything where a user would have to import ListBox. It seemed to have confused a user (#9555) so figured we remove mentions of it until it becomes relevant in S2.

✅ 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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• View the storybook
• View the S2 storybook
• View the S2 docs
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