Media queries do not support CSS custom properties (CSS variables), so we've had some useless variables lying around since shipping v4. This finally removes them and the associated documentation content that explained the situation. Fixes #29012.
This is required for Sass v3.5+ compatibility. See https://github.com/sass/sass/blob/stable/doc-src/SASS_CHANGELOG.md#backwards-incompatibilities----must-read and https://github.com/sass/sass/issues/2383
* Generate CSS variables See #23349 Supersedes #23446 * Ignore _root.scss for linting