Update dependency grunt-contrib-uglify to v5.2.1

[renovate[bot]]

This PR contains the following updates:

Package	Change	Age	Adoption	Passing	Confidence
grunt-contrib-uglify	5.1.0 -> 5.2.1

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Release Notes

gruntjs/grunt-contrib-uglify

### [`v5.2.1`](https://togithub.com/gruntjs/grunt-contrib-uglify/releases/v5.2.1) [Compare Source](https://togithub.com/gruntjs/grunt-contrib-uglify/compare/v5.1.0...v5.2.1) - Update Readme [`3c8d904`](https://togithub.com/gruntjs/grunt-contrib-uglify/commit/3c8d904) - update dependencies ([#​568](https://togithub.com/gruntjs/grunt-contrib-uglify/issues/568)) [`0850dcd`](https://togithub.com/gruntjs/grunt-contrib-uglify/commit/0850dcd) - Bump minimist from 1.2.5 to 1.2.6 ([#​567](https://togithub.com/gruntjs/grunt-contrib-uglify/issues/567)) [`c27ad5f`](https://togithub.com/gruntjs/grunt-contrib-uglify/commit/c27ad5f) - Fix documentation in relation to issue [#​565](https://togithub.com/gruntjs/grunt-contrib-uglify/issues/565) ([#​566](https://togithub.com/gruntjs/grunt-contrib-uglify/issues/566)) [`98b4c5f`](https://togithub.com/gruntjs/grunt-contrib-uglify/commit/98b4c5f) - Bump minimist from 1.2.5 to 1.2.6 ([#​563](https://togithub.com/gruntjs/grunt-contrib-uglify/issues/563)) [`7228446`](https://togithub.com/gruntjs/grunt-contrib-uglify/commit/7228446)

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