Bump vitepress from 1.6.3 to 1.6.4

Bumps [vitepress](https://github.com/vuejs/vitepress) from 1.6.3 to 1.6.4.
- [Release notes](https://github.com/vuejs/vitepress/releases)
- [Changelog](https://github.com/vuejs/vitepress/blob/v1.6.4/CHANGELOG.md)
- [Commits](vuejs/vitepress@v1.6.3...v1.6.4)

---
updated-dependencies:
- dependency-name: vitepress
  dependency-version: 1.6.4
  dependency-type: direct:development
  update-type: version-update:semver-patch
...

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

Author: dependabot[bot]