fix(deps): update dependency postcss to ^8.4.39

[renovate[bot]]

This PR contains the following updates:

Package	Change	Age	Adoption	Passing	Confidence
postcss (source)	^8.4.38 -> ^8.4.39

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Release Notes

postcss/postcss (postcss)

### [`v8.4.39`](https://togithub.com/postcss/postcss/blob/HEAD/CHANGELOG.md#8439) [Compare Source](https://togithub.com/postcss/postcss/compare/8.4.38...8.4.39) - Fixed `CssSyntaxError` types (by [@​romainmenke](https://togithub.com/romainmenke)).

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Size Report

Bundles

File	Size	Gzip	Brotli
runtime-dom.global.prod.js	89.4 kB	34.2 kB	30.8 kB
vue.global.prod.js	146 kB	53.6 kB	47.7 kB

Usages

Name	Size	Gzip	Brotli
createApp	51.3 kB	20.1 kB	18.3 kB
createSSRApp	54.7 kB	21.4 kB	19.5 kB
defineCustomElement	53.6 kB	20.9 kB	19 kB
overall	65 kB	25.1 kB	22.7 kB