Bump postcss and vue-loader

Bumps [postcss](https://github.com/postcss/postcss) and [vue-loader](https://github.com/vuejs/vue-loader). These dependencies needed to be updated together.

Updates `postcss` from 8.4.18 to 8.4.47
- [Release notes](https://github.com/postcss/postcss/releases)
- [Changelog](https://github.com/postcss/postcss/blob/main/CHANGELOG.md)
- [Commits](postcss/postcss@8.4.18...8.4.47)

Updates `vue-loader` from 15.10.0 to 17.4.2
- [Release notes](https://github.com/vuejs/vue-loader/releases)
- [Changelog](https://github.com/vuejs/vue-loader/blob/main/CHANGELOG.md)
- [Commits](vuejs/vue-loader@v15.10.0...v17.4.2)

---
updated-dependencies:
- dependency-name: postcss
  dependency-type: direct:development
- dependency-name: vue-loader
  dependency-type: direct:development
...

Signed-off-by: dependabot[bot] <[email protected]>