Replace indexed loop with for-each java5 syntax (#6335)

* Replace indexed loop with for-each java5 syntax

* Restore code as per @akarnokd code review

* Keep empty lines as per @akarnokd code review

Author: igor-suhorukov

src/main/java/io/reactivex/internal/operators/parallel/ParallelJoin.java

@@ -110,15 +110,13 @@ public void cancel() {
         }
 
         void cancelAll() {
-            for (int i = 0; i < subscribers.length; i++) {
-                JoinInnerSubscriber<T> s = subscribers[i];
+            for (JoinInnerSubscriber<T> s : subscribers) {
                 s.cancel();
             }
         }
 
         void cleanup() {
-            for (int i = 0; i < subscribers.length; i++) {
-                JoinInnerSubscriber<T> s = subscribers[i];
+            for (JoinInnerSubscriber<T> s : subscribers) {
                 s.queue = null;
             }
         }