chore(deps): bump postcss from 8.2.10 to 8.4.5 in /packages/semantic-ui

Bumps [postcss](https://github.com/postcss/postcss) from 8.2.10 to 8.4.5.
- [Release notes](https://github.com/postcss/postcss/releases)
- [Changelog](https://github.com/postcss/postcss/blob/main/CHANGELOG.md)
- [Commits](postcss/postcss@8.2.10...8.4.5)

---
updated-dependencies:
- dependency-name: postcss
  dependency-type: indirect
...

Signed-off-by: dependabot[bot] <support@github.com>