Iterator[A] does not take parameters

Fix by removing parens.

Author: ashawley

src/main/scala/org/scalacheck/Cogen.scala

@@ -118,7 +118,7 @@ object Cogen extends CogenArities with CogenLowPriority {
     Cogen[String].contramap(_.name)
 
   implicit def cogenList[A: Cogen]: Cogen[List[A]] =
-    Cogen.it(_.iterator())
+    Cogen.it(_.iterator)
 
   implicit def cogenVector[A: Cogen]: Cogen[Vector[A]] =
     Cogen.it(_.iterator)