chore(deps-dev): bump mocha from 5.2.0 to 6.2.0

Bumps [mocha](https://github.com/mochajs/mocha) from 5.2.0 to 6.2.0.
- [Release notes](https://github.com/mochajs/mocha/releases)
- [Changelog](https://github.com/mochajs/mocha/blob/master/CHANGELOG.md)
- [Commits](mochajs/mocha@v5.2.0...v6.2.0)

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

Author: dependabot-preview[bot]