chore(deps): bump postcss and parcel

Removes [postcss](https://github.com/postcss/postcss). It's no longer used after updating ancestor dependency [parcel](https://github.com/parcel-bundler/parcel). These dependencies need to be updated together.


Removes `postcss`

Updates `parcel` from 2.0.0-nightly.640 to 2.9.3
- [Release notes](https://github.com/parcel-bundler/parcel/releases)
- [Changelog](https://github.com/parcel-bundler/parcel/blob/v2/CHANGELOG.md)
- [Commits](https://github.com/parcel-bundler/parcel/commits/v2.9.3)

---
updated-dependencies:
- dependency-name: postcss
  dependency-type: indirect
- dependency-name: parcel
  dependency-type: direct:development
...

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