chore(deps): update dependency mocha to v6

[renovate[bot]]

This PR contains the following updates:

Package	Type	Update	Change	References
mocha	devDependencies	major	^5.2.0 -> ^6.0.0	homepage, source

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Release Notes

mochajs/mocha

### [`v6.0.0`](https://togithub.com/mochajs/mocha/blob/master/CHANGELOG.md#​600--2019-02-18) [Compare Source](https://togithub.com/mochajs/mocha/compare/v5.2.0...v6.0.0) #### :tada: Enhancements - [#​3726](https://togithub.com/mochajs/mocha/issues/3726): Add ability to unload files from `require` cache ([**@​plroebuck**](https://togithub.com/plroebuck)) #### :bug: Fixes - [#​3737](https://togithub.com/mochajs/mocha/issues/3737): Fix falsy values from options globals ([**@​plroebuck**](https://togithub.com/plroebuck)) - [#​3707](https://togithub.com/mochajs/mocha/issues/3707): Fix encapsulation issues for `Suite#_onlyTests` and `Suite#_onlySuites` ([**@​vkarpov15**](https://togithub.com/vkarpov15)) - [#​3711](https://togithub.com/mochajs/mocha/issues/3711): Fix diagnostic messages dealing with plurality and markup of output ([**@​plroebuck**](https://togithub.com/plroebuck)) - [#​3723](https://togithub.com/mochajs/mocha/issues/3723): Fix "reporter-option" to allow comma-separated options ([**@​boneskull**](https://togithub.com/boneskull)) - [#​3722](https://togithub.com/mochajs/mocha/issues/3722): Fix code quality and performance of `lookupFiles` and `files` ([**@​plroebuck**](https://togithub.com/plroebuck)) - [#​3650](https://togithub.com/mochajs/mocha/issues/3650), [#​3654](https://togithub.com/mochajs/mocha/issues/3654): Fix noisy error message when no files found ([**@​craigtaub**](https://togithub.com/craigtaub)) - [#​3632](https://togithub.com/mochajs/mocha/issues/3632): Tests having an empty title are no longer confused with the "root" suite ([**@​juergba**](https://togithub.com/juergba)) - [#​3666](https://togithub.com/mochajs/mocha/issues/3666): Fix missing error codes ([**@​vkarpov15**](https://togithub.com/vkarpov15)) - [#​3684](https://togithub.com/mochajs/mocha/issues/3684): Fix exiting problem in Node.js v11.7.0+ ([**@​addaleax**](https://togithub.com/addaleax)) - [#​3691](https://togithub.com/mochajs/mocha/issues/3691): Fix `--delay` (and other boolean options) not working in all cases ([**@​boneskull**](https://togithub.com/boneskull)) - [#​3692](https://togithub.com/mochajs/mocha/issues/3692): Fix invalid command-line argument usage not causing actual errors ([**@​boneskull**](https://togithub.com/boneskull)) - [#​3698](https://togithub.com/mochajs/mocha/issues/3698), [#​3699](https://togithub.com/mochajs/mocha/issues/3699): Fix debug-related Node.js options not working in all cases ([**@​boneskull**](https://togithub.com/boneskull)) - [#​3700](https://togithub.com/mochajs/mocha/issues/3700): Growl notifications now show the correct number of tests run ([**@​outsideris**](https://togithub.com/outsideris)) - [#​3686](https://togithub.com/mochajs/mocha/issues/3686): Avoid potential ReDoS when diffing large objects ([**@​cyjake**](https://togithub.com/cyjake)) - [#​3715](https://togithub.com/mochajs/mocha/issues/3715): Fix incorrect order of emitted events when used programmatically ([**@​boneskull**](https://togithub.com/boneskull)) - [#​3706](https://togithub.com/mochajs/mocha/issues/3706): Fix regression wherein `--reporter-option`/`--reporter-options` did not support comma-separated key/value pairs ([**@​boneskull**](https://togithub.com/boneskull)) #### :book: Documentation - [#​3652](https://togithub.com/mochajs/mocha/issues/3652): Switch from Jekyll to Eleventy ([**@​Munter**](https://togithub.com/Munter)) #### :nut_and_bolt: Other - [#​3677](https://togithub.com/mochajs/mocha/issues/3677): Add error objects for createUnsupportedError and createInvalidExceptionError ([**@​boneskull**](https://togithub.com/boneskull)) - [#​3733](https://togithub.com/mochajs/mocha/issues/3733): Removed unnecessary processing in post-processing hook ([**@​wanseob**](https://togithub.com/wanseob)) - [#​3730](https://togithub.com/mochajs/mocha/issues/3730): Update nyc to latest version ([**@​coreyfarrell**](https://togithub.com/coreyfarrell)) - [#​3648](https://togithub.com/mochajs/mocha/issues/3648), [#​3680](https://togithub.com/mochajs/mocha/issues/3680): Fixes to support latest versions of [unexpected](https://npm.im/unexpected) and [unexpected-sinon](https://npm.im/unexpected-sinon) ([**@​sunesimonsen**](https://togithub.com/sunesimonsen)) - [#​3638](https://togithub.com/mochajs/mocha/issues/3638): Add meta tag to site ([**@​MartijnCuppens**](https://togithub.com/MartijnCuppens)) - [#​3653](https://togithub.com/mochajs/mocha/issues/3653): Fix parts of test suite failing to run on Windows ([**@​boneskull**](https://togithub.com/boneskull))

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