Remove Extra Synchronization

The use of flatMap/mergeMap already synchronizes.

Author: benjchristensen

rxjava-core/src/main/java/rx/operators/OperationParallel.java

@@ -46,13 +46,13 @@ public Integer call(T t) {
                         return i.incrementAndGet() % s.degreeOfParallelism();
                     }
 
-                }).flatMap(new Func1<GroupedObservable<Integer, T>, Observable<R>>() {
+                }).mergeMap(new Func1<GroupedObservable<Integer, T>, Observable<R>>() {
 
                     @Override
                     public Observable<R> call(GroupedObservable<Integer, T> group) {
                         return f.call(group.observeOn(s));
                     }
-                }).synchronize();
+                });
             }
         });
     }