fixup! adds groupUntilChanged extension method on scala.collection.Iterator

inlines `key` since it is only used once

Author: jeantil

src/main/scala/scala/collection/decorators/IteratorDecorator.scala

@@ -102,10 +102,9 @@ class IteratorDecorator[A](val `this`: Iterator[A]) extends AnyVal {
         hd match {
           case None => Iterator.empty.next()
           case Some(head) =>
-            val key = f(head)
             hd = `this`.nextOption()
             var seq = mutable.Buffer(head)
-            while (hd.exists(el => f(el) == key)) {
+            while (hd.exists(el => f(el) == f(head))) {
               seq = seq ++ hd
               hd = `this`.nextOption()
             }