Bump y18n from 4.0.0 to 4.0.1 in /test

Bumps [y18n](https://github.com/yargs/y18n) from 4.0.0 to 4.0.1.
- [Release notes](https://github.com/yargs/y18n/releases)
- [Changelog](https://github.com/yargs/y18n/blob/master/CHANGELOG.md)
- [Commits](https://github.com/yargs/y18n/commits)

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Author: dependabot[bot]