Update dependency mocha to v8.1.3

[renovate[bot]]

This PR contains the following updates:

Package	Type	Update	Change
mocha (source)	devDependencies	patch	8.1.1 -> 8.1.3

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Release Notes

mochajs/mocha

### [`v8.1.3`](https://togithub.com/mochajs/mocha/blob/master/CHANGELOG.md#​813--2020-08-28) [Compare Source](https://togithub.com/mochajs/mocha/compare/v8.1.2...v8.1.3) #### :bug: Fixes - [#​4425](https://togithub.com/mochajs/mocha/issues/4425): Restore `Mocha.utils.lookupFiles()` and Webpack compatibility (both broken since v8.1.0); `Mocha.utils.lookupFiles()` is now **deprecated** and will be removed in the next major revision of Mocha; use `require('mocha/lib/cli').lookupFiles` instead ([**@​boneskull**](https://togithub.com/boneskull)) ### [`v8.1.2`](https://togithub.com/mochajs/mocha/blob/master/CHANGELOG.md#​812--2020-08-25) [Compare Source](https://togithub.com/mochajs/mocha/compare/v8.1.1...v8.1.2) #### :bug: Fixes - [#​4418](https://togithub.com/mochajs/mocha/issues/4418): Fix command-line flag incompatibility in forthcoming Node.js v14.9.0 ([**@​boneskull**](https://togithub.com/boneskull)) - [#​4401](https://togithub.com/mochajs/mocha/issues/4401): Fix missing global variable in browser ([**@​irrationnelle**](https://togithub.com/irrationnelle)) #### :lock: Security Fixes - [#​4396](https://togithub.com/mochajs/mocha/issues/4396): Update many dependencies ([**@​GChuf**](https://togithub.com/GChuf)) #### :book: Documentation - Various fixes by [**@​sujin-park**](https://togithub.com/sujin-park), [**@​wwhurin**](https://togithub.com/wwhurin) & [**@​Donghoon759**](https://togithub.com/Donghoon759)

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