MixedObserversTest#testAsyncObserversCalledInDifferentThread wrongly assumes that async observers are notified in the same thread

Following assertion needs to be removed or changed:

assertEquals(MassachusettsInstituteObserver.threadId.get(), StandfordUniversityObserver.threadId.get()); 

because the corresponding TCK assertion states:

All the resolved asynchronous observers are called in one or more different threads.