chore: simplifying keyboard navigation docs copy

[LFDanLu]

followup from #10159

✅ 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:

Check that there are placeholder in the textfields for RAC Table/Gridlist and S2 TableView/ListView keyboard navigation docs. That docs section should be simpler now too

🧢 Your Project:

RSP