build(deps-dev): bump mocha from 6.0.2 to 6.1.1

Bumps [mocha](https://github.com/mochajs/mocha) from 6.0.2 to 6.1.1.
- [Release notes](https://github.com/mochajs/mocha/releases)
- [Changelog](https://github.com/mochajs/mocha/blob/master/CHANGELOG.md)
- [Commits](mochajs/mocha@v6.0.2...v6.1.1)

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

Author: dependabot-support