Bump vuex from 3.1.3 to 3.4.0

Bumps [vuex](https://github.com/vuejs/vuex) from 3.1.3 to 3.4.0.
- [Release notes](https://github.com/vuejs/vuex/releases)
- [Changelog](https://github.com/vuejs/vuex/blob/dev/CHANGELOG.md)
- [Commits](https://github.com/vuejs/vuex/compare/v3.1.3...v3.4.0

)

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