chore(deps): update dependency postcss-nested to v6

[renovate[bot]]

This PR contains the following updates:

Package	Change	Age	Adoption	Passing	Confidence
postcss-nested	^5.0.6 -> ^6.0.0

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Release Notes

postcss/postcss-nested

### [`v6.0.0`](https://togithub.com/postcss/postcss-nested/compare/5.0.6...6.0.0) [Compare Source](https://togithub.com/postcss/postcss-nested/compare/5.0.6...6.0.0)

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