Update dependency grunt-contrib-cssmin to v5

[renovate[bot]]

This PR contains the following updates:

Package	Change	Age	Adoption	Passing	Confidence
grunt-contrib-cssmin	^4.0.0 -> ^5.0.0

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Release Notes

gruntjs/grunt-contrib-cssmin (grunt-contrib-cssmin)

### [`v5.0.0`](https://togithub.com/gruntjs/grunt-contrib-cssmin/releases/tag/v5.0.0) [Compare Source](https://togithub.com/gruntjs/grunt-contrib-cssmin/compare/v4.0.0...v5.0.0) - Update dependencies. - Drop Node.js < 14 support.

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Configuration

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