Bump defu in /docs in the npm_and_yarn group across 1 directory

Bumps the npm_and_yarn group with 1 update in the /docs directory: [defu](https://github.com/unjs/defu).


Updates `defu` from 6.1.4 to 6.1.6
- [Release notes](https://github.com/unjs/defu/releases)
- [Changelog](https://github.com/unjs/defu/blob/main/CHANGELOG.md)
- [Commits](unjs/defu@v6.1.4...v6.1.6)

---
updated-dependencies:
- dependency-name: defu
  dependency-version: 6.1.6
  dependency-type: indirect
  dependency-group: npm_and_yarn
...

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

Author: dependabot[bot]