Describe the bug

In 2.23 the CSS example that highlights disconnected items in red causes all items to be red.
/* Highlight disconnected lines in red */

:not([subject], :is(line, box, ellipse, commentline)) {
color: firebrick;
}

To Reproduce

Steps to reproduce the behavior:
Apply the above example CSS lines to your CSS.
See error

Expected behavior

Screenshots

If applicable, add screenshots to help explain your problem.

OS

• Linux (Please put in notes the specific distro)
• [ x] macOS
• Windows

Version

Version of Gaphor: 2.23

Additional information

Not sure if this points to any deeper issues with recent changes to CSS, or just needs updating/removing as an example CSS snippet in the documentation.