Update dependency grunt-shell to v3

[renovate[bot]]

This PR contains the following updates:

Package	Type	Update	Change	References
grunt-shell	devDependencies	major	2.1.0 -> 3.0.1	source

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Release Notes

sindresorhus/grunt-shell

### [`v3.0.1`](https://renovatebot.com/gh/sindresorhus/grunt-shell/releases/v3.0.1) [Compare Source](https://renovatebot.com/gh/sindresorhus/grunt-shell/compare/v3.0.0...v3.0.1) - Fix broken `chalk` upgrade [`1361a33`](https://renovatebot.com/gh/sindresorhus/grunt-shell/commit/1361a33) ### [`v3.0.0`](https://renovatebot.com/gh/sindresorhus/grunt-shell/releases/v3.0.0) [Compare Source](https://renovatebot.com/gh/sindresorhus/grunt-shell/compare/v2.1.0...v3.0.0) Breaking: - Require Node.js >=6 and Grunt >=1 [`62cdda5`](https://renovatebot.com/gh/sindresorhus/grunt-shell/commit/62cdda5) Other: - Allow functions as shorthand commands ([#​118](https://renovatebot.com/gh/sindresorhus/grunt-shell/issues/118)) [`86680b4`](https://renovatebot.com/gh/sindresorhus/grunt-shell/commit/86680b4)

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