Upgrade `tsx` in the `framework-fastify` example to be Node 18 compat

[jpwilliams]

Summary

Small bump of tsx in examples/framework-fastify to ensure it works with Node 18.19.0.

Checklist

• [ ] ~Added a docs PR that references this PR~ N/A
• [ ] ~Added unit/integration tests~ N/A
• [x] Added changesets if applicable

Related

• privatenumber/tsx#421

[changeset-bot[bot]]

⚠️ No Changeset found

Latest commit: b26851bc64a2e6252626df17637c1828904503e7

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