(docs deps): Bump undici from 6.21.1 to 6.21.3 in the npm_and_yarn group

Bumps the npm_and_yarn group with 1 update: [undici](https://github.com/nodejs/undici).


Updates `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
  dependency-group: npm_and_yarn
...

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]