Bump undici from 6.21.1 to 6.21.3 in /utils/fe-version-validator

Bumps [undici](https://github.com/nodejs/undici) from 6.21.1 to 6.21.3.
- [Release notes](https://github.com/nodejs/undici/releases)
- [Commits](nodejs/undici@v6.21.1...v6.21.3)

---
updated-dependencies:
- dependency-name: undici
  dependency-version: 6.21.3
  dependency-type: indirect
...

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]