math.factorials: cleanup using.

extra/math/factorials/factorials.factor

@@ -1,8 +1,8 @@
 ! Copyright (C) 2013 John Benediktsson
 ! See http://factorcode.org/license.txt for BSD license
 
-USING: combinators combinators.short-circuit kernel locals math
-math.functions math.ranges memoize sequences ;
+USING: combinators kernel math math.functions math.ranges
+memoize sequences ;
 
 IN: math.factorials