SCSSLint: Bump to 0.23.1

New rules have been added that we can take advantage of
SCSSLint: Combine duplicate root selectors
SCSSLint: Remove unnecessary units

Sass already converts floats for division
SCSSLint: Apply PropertySort order

Basic alpha sorting for now
- Greyscale hack in tabs Sass requires it to be excluded
- Fixed but in slider SCSS with missing `@` for keyframes value
Merge pull request #5278 from nschonni/scss-lint-0.23.1

Scss lint 0.23.1