Bump undici from 5.28.3 to 5.28.4 in /example

Bumps [undici](https://github.com/nodejs/undici) from 5.28.3 to 5.28.4.
- [Release notes](https://github.com/nodejs/undici/releases)
- [Commits](nodejs/undici@v5.28.3...v5.28.4)

---
updated-dependencies:
- dependency-name: undici
  dependency-type: indirect
...

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