Fix check that would always be false (#6045)

Checking `BlockingSubscriber.TERMINATED` (`new Object()`) against `o` would always be false since `o` is a publisher. Since `v` comes from the queue this is presumably the variable that should be checked.

However the check might even be redundant with this change since that variable can only appear in the queue after the subscriber has been cancelled. I am not familiar enough with the memory model to say whether the object appearing in the queue implies the cancelled subscriber is visible.

Author: Kiskae

src/main/java/io/reactivex/internal/operators/flowable/FlowableBlockingSubscribe.java

@@ -63,7 +63,7 @@ public static <T> void subscribe(Publisher<? extends T> o, Subscriber<? super T>
                 if (bs.isCancelled()) {
                     break;
                 }
-                if (o == BlockingSubscriber.TERMINATED
+                if (v == BlockingSubscriber.TERMINATED
                         || NotificationLite.acceptFull(v, subscriber)) {
                     break;
                 }