[SYCL] Fix flaky race in StreamBufferDeallocation unit test (#7855)

The Scheduler/GraphCleanup::StreamBufferDeallocation test attempts to
'precheck' that the node count is 2 before the cleanup completes (when
it is once again tested and confirmed to be 0). But this 'precheck' is
racing on Windows. While it is OK about 85% of the time, in the other
15% of runs the clean-up has already begun and there is just one node,
or none. This fix simply removes the 'precheck' as it is not central to
the test.

Signed-off-by: Perkins, Chris <[email protected]>

Author: cperkinsintel

sycl/unittests/scheduler/GraphCleanup.cpp

@@ -344,8 +344,6 @@ TEST_F(SchedulerTest, StreamBufferDeallocation) {
     EventImplPtr = MSPtr->addCG(std::move(CG), QueueImplPtr);
   }
 
-  // Both buffers should have been sent to the deferred release.
-  ASSERT_EQ(MSPtr->MDeferredMemObjRelease.size(), 2u);
   // The buffers should have been released with graph cleanup once the work is
   // finished.
   EventImplPtr->wait(EventImplPtr);