Update mocha requirement from ^5.2.0 to ^6.1.4
Update mocha requirement from ^5.2.0 to ^6.1.4

Updates the requirements on [mocha](https://github.com/mochajs/mocha) to permit the latest version.
- [Release notes](https://github.com/mochajs/mocha/releases)
- [Changelog](https://github.com/mochajs/mocha/blob/master/CHANGELOG.md)
- [Commits](https://github.com/mochajs/mocha/compare/v5.2.0...v6.1.4)

Signed-off-by: dependabot[bot] <5bdcd3c0d4d24ae3e71b3b452a024c6324c7e4bb@dependabot.com>
Apollon77/smartmeter-obis