Fix missing method error in SASS lexer (#2125)

Author: tancnle

lib/rouge/lexers/sass/common.rb

@@ -155,7 +155,7 @@ class SassCommon < RegexLexer
       state :attr_common do
         mixin :has_interp
         rule id do |m|
-          if CSS.attributes.include? m[0]
+          if CSS.properties.include? m[0]
             token Name::Label
           else
             token Name::Attribute