Upon hovering the closing button of a modal in Moodle (e.g. "Add an activity or resource") there's an round edged gradient background.

STEPS TO REPRODUCE

1. Go to a course
2. Switch to the editing mode
3. Click the "Add an activity or resource" link in a course section.
4. Hover the closing button of the opened modal

WHAT YOU EXPECTED

A nice hover effect respecting the CI/CD

WHAT ACTUALLY HAPPENS

See the attached screenshot.