Convert SCSS to module.css

## Description

After our decision to use CSS modules, we should convert [Infobox.module.scss](https://github.com/openmcp-project/ui-frontend/blob/f0d316bbe9d912514a718c408d07c37846e9a59b/src/components/Ui/Infobox/Infobox.module.scss) to a CSS module.

After this, we can uninstall SASS support.

ToDo:
- [x] Convert Infobox.module.scss to Infobox.module.css
- [x] Uninstall SASS