Update dependency autoprefixer to v10.0.4

[renovate[bot]]

This PR contains the following updates:

Package	Change	Age	Adoption	Passing	Confidence
autoprefixer	10.0.2 -> 10.0.4

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Release Notes

postcss/autoprefixer

### [`v10.0.4`](https://togithub.com/postcss/autoprefixer/blob/master/CHANGELOG.md#​1004) [Compare Source](https://togithub.com/postcss/autoprefixer/compare/10.0.3...10.0.4) - Fixed `Cannot read property 'proxyOf' of undefined` error (by Igor Kamyshev). ### [`v10.0.3`](https://togithub.com/postcss/autoprefixer/blob/master/CHANGELOG.md#​1003) [Compare Source](https://togithub.com/postcss/autoprefixer/compare/10.0.2...10.0.3) - Fixed `substract` to `subtract` value for `mask-composite` (by Michelle Enos).

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