Update dependency mocha to v6.2.1

[renovate[bot]]

This PR contains the following updates:

Package	Type	Update	Change
mocha (source)	devDependencies	patch	6.2.0 -> 6.2.1

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Release Notes

mochajs/mocha

### [`v6.2.1`](https://togithub.com/mochajs/mocha/blob/master/CHANGELOG.md#​621--2019-09-29) [Compare Source](https://togithub.com/mochajs/mocha/compare/v6.2.0...v6.2.1) #### :bug: Fixes - [#​3955](https://togithub.com/mochajs/mocha/issues/3955): tty.getWindowSize is not a function inside a "worker_threads" worker ([**@​1999**](https://togithub.com/1999)) - [#​3970](https://togithub.com/mochajs/mocha/issues/3970): remove extraGlobals() ([**@​juergba**](https://togithub.com/juergba)) - [#​3984](https://togithub.com/mochajs/mocha/issues/3984): Update yargs-unparser to v1.6.0 ([**@​juergba**](https://togithub.com/juergba)) - [#​3983](https://togithub.com/mochajs/mocha/issues/3983): Package 'esm': spawn child-process for correct loading ([**@​juergba**](https://togithub.com/juergba)) - [#​3986](https://togithub.com/mochajs/mocha/issues/3986): Update yargs to v13.3.0 and yargs-parser to v13.1.1 ([**@​juergba**](https://togithub.com/juergba)) #### :book: Documentation - [#​3886](https://togithub.com/mochajs/mocha/issues/3886): fix styles on mochajs.org ([**@​outsideris**](https://togithub.com/outsideris)) - [#​3966](https://togithub.com/mochajs/mocha/issues/3966): Remove jsdoc index.html placeholder from eleventy file structure and fix broken link in jsdoc tutorial ([**@​Munter**](https://togithub.com/Munter)) - [#​3765](https://togithub.com/mochajs/mocha/issues/3765): Add Matomo to website ([**@​MarioDiaz98**](https://togithub.com/MarioDiaz98)) - [#​3947](https://togithub.com/mochajs/mocha/issues/3947): Clarify effect of .skip() ([**@​oliversalzburg**](https://togithub.com/oliversalzburg))

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