Revert "Give the Sass Lexer a lookahead of 2 for keyword argument sup…

…port."

This reverts commit f73854c.

lib/sass/script/lexer.rb

@@ -169,16 +169,6 @@ def unpeek!
         @scanner.pos = @tok.pos if @tok
       end
 
-      # Rewinds the underlying StringScanner
-      # to before the previous token returned by \{#next}.
-      def return_previous!
-        if @prev
-          @scanner.pos = @prev.pos
-          @prev = nil
-          @tok = nil
-        end
-      end
-
       # @return [Boolean] Whether or not there's more source text to lex.
       def done?
         whitespace unless after_interpolation? && @interpolation_stack.last

lib/sass/script/parser.rb

@@ -404,10 +404,6 @@ def try_tok(*names)
         peeked && names.include?(peeked.type) && @lexer.next
       end
 
-      def return_tok!
-        @lexer.return_previous!
-      end
-
       def assert_done
         return if @lexer.done?
         @lexer.expected!(EXPR_NAMES[:default])