Remove configuration of theme sass files from Core (#7290)

Merge pull request 7290

lib/jekyll/theme.rb

@@ -10,7 +10,6 @@ module Jekyll
       @name = name.downcase.strip
       Jekyll.logger.debug "Theme:", name
       Jekyll.logger.debug "Theme source:", root
-      configure_sass
     end
 
     def root
@@ -38,13 +37,6 @@ module Jekyll
       @assets_path ||= path_for "assets"
     end
 
-    def configure_sass
-      return unless sass_path
-
-      External.require_with_graceful_fail("sass") unless defined?(Sass)
-      Sass.load_paths << sass_path
-    end
-
     def runtime_dependencies
       gemspec.runtime_dependencies
     end