Resolve Sass division deprecation warning

Signed-off-by: Georg Pfuetzenreuter mail@georg-pfuetzenreuter.net

Hi,

this resolves

Deprecation Warning: Using / for division outside of calc() is deprecated and will be removed in Dart Sass 2.0.0.

in accordance with

https://sass-lang.com/documentation/breaking-changes/slash-div

Best, Georg