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## Summary
<!-- What's the purpose of the change? What does it do, and why? -->
The note about rules being in preview was not being displayed for legacy
nursery rules.
Adds a link to the new preview documentation as well.
## Test Plan
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Built locally and checked a nursery rule e.g.
http://127.0.0.1:8000/ruff/rules/no-indented-block-comment/
528f386131