Fix formatting/typo

xcsp-lang.lisp

@@ -15,7 +15,7 @@
   (:lambda (expr)
     (string= expr "true")))
 
-(defrule identifier (+( character-ranges (#\A #\Z) (#\a #\z) (#\0 #\9)))
+(defrule identifier (+ (character-ranges (#\A #\Z) (#\a #\z) (#\0 #\9)))
   (:text t)
   (:lambda (text)
     (symbolicate (string-upcase text))))