Update sassc to version 2.4.0

Author: depfu[bot]

Gemfile

@@ -11,7 +11,7 @@ gem 'nokogiri', '~> 1.10'
 
 group :jekyll_plugins do
   gem 'jemoji'
-  gem 'sassc', '~> 2.1.0'
+  gem 'sassc', '~> 2.4.0'
   gem "jekyll-feed", "~> 0.6"
   gem 'jekyll-assets', :git => 'https://github.com/jekyll/jekyll-assets.git'
   gem 'jekyll-sitemap', '~> 1.3.1'