build(deps): bump postcss-selector-parser and @vue/cli-service in /ui

Bumps [postcss-selector-parser](https://github.com/postcss/postcss-selector-parser) to 6.1.5 and updates ancestor dependency [@vue/cli-service](https://github.com/vuejs/vue-cli/tree/HEAD/packages/@vue/cli-service). These dependencies need to be updated together.


Updates `postcss-selector-parser` from 3.1.2 to 6.1.5
- [Release notes](https://github.com/postcss/postcss-selector-parser/releases)
- [Changelog](https://github.com/postcss/postcss-selector-parser/blob/6.1.5/CHANGELOG.md)
- [Commits](postcss/postcss-selector-parser@v3.1.2...6.1.5)

Updates `@vue/cli-service` from 4.5.19 to 5.0.9
- [Release notes](https://github.com/vuejs/vue-cli/releases)
- [Changelog](https://github.com/vuejs/vue-cli/blob/dev/CHANGELOG.md)
- [Commits](https://github.com/vuejs/vue-cli/commits/v5.0.9/packages/@vue/cli-service)

---
updated-dependencies:
- dependency-name: postcss-selector-parser
  dependency-version: 6.1.5
  dependency-type: indirect
- dependency-name: "@vue/cli-service"
  dependency-version: 5.0.9
  dependency-type: direct:development
...

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Author: dependabot[bot]