Bump unhead and nuxt

Bumps [unhead](https://github.com/unjs/unhead/tree/HEAD/packages/unhead) to 2.1.12 and updates ancestor dependency [nuxt](https://github.com/nuxt/nuxt/tree/HEAD/packages/nuxt). These dependencies need to be updated together.


Updates `unhead` from 1.11.7 to 2.1.12
- [Release notes](https://github.com/unjs/unhead/releases)
- [Commits](https://github.com/unjs/unhead/commits/v2.1.12/packages/unhead)

Updates `nuxt` from 3.13.2 to 3.21.2
- [Release notes](https://github.com/nuxt/nuxt/releases)
- [Commits](https://github.com/nuxt/nuxt/commits/v3.21.2/packages/nuxt)

---
updated-dependencies:
- dependency-name: unhead
  dependency-version: 2.1.12
  dependency-type: indirect
- dependency-name: nuxt
  dependency-version: 3.21.2
  dependency-type: direct:production
...

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Author: dependabot[bot]