Bump autoprefixer from 10.4.0 to 10.4.21

Bumps [autoprefixer](https://github.com/postcss/autoprefixer) from 10.4.0 to 10.4.21.
- [Release notes](https://github.com/postcss/autoprefixer/releases)
- [Changelog](https://github.com/postcss/autoprefixer/blob/main/CHANGELOG.md)
- [Commits](https://github.com/postcss/autoprefixer/compare/10.4.0...10.4.21

)

---
updated-dependencies:
- dependency-name: autoprefixer
  dependency-version: 10.4.21
  dependency-type: direct:development
  update-type: version-update:semver-patch
...

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