build(deps): bump defu from 6.1.4 to 6.1.6 in /site

Bumps [defu](https://github.com/unjs/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
...

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

Author: dependabot[bot]