Update dependency del to v6

[renovate[bot]]

This PR contains the following updates:

Package	Type	Update	Change
del	devDependencies	major	5.1.0 -> 6.0.0

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Release Notes

sindresorhus/del

### [`v6.0.0`](https://togithub.com/sindresorhus/del/releases/v6.0.0) [Compare Source](https://togithub.com/sindresorhus/del/compare/v5.1.0...v6.0.0) ##### Breaking - Require Node.js 10 [`6c99805`](https://togithub.com/sindresorhus/del/commit/6c99805) ##### Improvements - Update dependencies [`6c99805`](https://togithub.com/sindresorhus/del/commit/6c99805)

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