Problem/Motivation
This is part of the CSS modernization initiative.
Steps to reproduce
The stylesheet at https://git.drupalcode.org/project/drupal/-/blob/10.0.x/core/themes/claro/css/components/fieldset.pcss.css needs to be refactored to make use of modern CSS and Drupal core's PostCSS tooling.
Proposed resolution
Use CSS Logical Properties where appropriate
Use CSS nesting where appropriate
Remaining tasks
We need two patches. One for Drupal 9.5.x and one for Drupal 10.0.x
We need a followup issue to refactor this component in Drupal 10.0.x to make use of component-level CSS custom properties and remove IE specific style definitions.
User interface changes
None. There should be no visual differences.