fix(deps): bump vue from 3.4.15 to 3.4.21 in /example

Bumps [vue](https://github.com/vuejs/core) from 3.4.15 to 3.4.21.
- [Release notes](https://github.com/vuejs/core/releases)
- [Changelog](https://github.com/vuejs/core/blob/main/CHANGELOG.md)
- [Commits](vuejs/core@v3.4.15...v3.4.21)

---
updated-dependencies:
- dependency-name: vue
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

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