fix(deps): bump @vue/composition-api from 0.6.3 to 0.6.4

Bumps [@vue/composition-api](https://github.com/vuejs/composition-api) from 0.6.3 to 0.6.4.
- [Release notes](https://github.com/vuejs/composition-api/releases)
- [Changelog](https://github.com/vuejs/composition-api/blob/v0.6.4/CHANGELOG.md)
- [Commits](vuejs/composition-api@v0.6.3...v0.6.4)

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