disable CooperativeBlockingCanCreateThreadsFaster on OSX (#66988)

src/libraries/System.Threading.ThreadPool/tests/ThreadPoolTests.cs

@@ -906,6 +906,7 @@ public static void ThreadPoolThreadCreationDoesNotTransferExecutionContext()
         }
 
         [ConditionalFact(nameof(IsThreadingAndRemoteExecutorSupported))]
+        [ActiveIssue("https://github.com/dotnet/runtime/issues/66852", TestPlatforms.OSX)]
         public static void CooperativeBlockingCanCreateThreadsFaster()
         {
             // Run in a separate process to test in a clean thread pool environment such that work items queued by the test