Update dependency gulp-useref to v4

[renovate[bot]]

This PR contains the following updates:

Package	Type	Update	Change
gulp-useref	devDependencies	major	^3.1.3 -> ^4.0.0

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Release Notes

jonkemp/gulp-useref

### [`v4.0.0`](https://togithub.com/jonkemp/gulp-useref/compare/v3.1.6...v4.0.0) [Compare Source](https://togithub.com/jonkemp/gulp-useref/compare/v3.1.6...v4.0.0)

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