chore: update deprecated division syntax to use math.div
BREAKING CHANGE: This makes GitLab UI's stylesheets incompatible with `libsass` which does not support `math.div`. Consuming the stylesheets now requires `dart-sass`.
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mentioned in commit bd5e6a89 
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mentioned in merge request gitlab!156682 (merged) 
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mentioned in merge request gitlab-org/editor-extensions/gitlab-jetbrains-plugin!590 (closed) 
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mentioned in merge request status-page!903 
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mentioned in merge request gitlab!156944 (closed) 
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mentioned in merge request gitlab-org/editor-extensions/gitlab-jetbrains-plugin!601 (closed) 
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mentioned in merge request gitlab-org/editor-extensions/gitlab-jetbrains-plugin!603 (merged) 
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mentioned in merge request gitlab-org/editor-extensions/gitlab-jetbrains-plugin!604 (closed) 
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mentioned in merge request gitlab-org/gitlab-services/design.gitlab.com!3905 (merged) 
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mentioned in merge request gitlab-org/frontend/pajamas-adoption-scanner!338 (merged) 
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mentioned in merge request gitlab-org/frontend/playground/accessibility-scanner!40 (merged) 
