Fix erroneous use of TaskContinuationOptions in ThreadUtils.cs

This was supposed to be TaskCreationOptions.

src/Microsoft.ML.Core/Utilities/ThreadUtils.cs

@@ -58,7 +58,7 @@ private static Task QueueAsync(Delegate threadStart, object state)
                 // Call sites only care about completion, not about the distinction between
                 // success and failure and do not expect exceptions to be propagated in this manner,
                 // so only SetResult is used.
-                var tcs = new TaskCompletionSource<bool>(TaskContinuationOptions.RunContinuationsAsynchronously);
+                var tcs = new TaskCompletionSource<bool>(TaskCreationOptions.RunContinuationsAsynchronously);
 
                 // Queue the work for a thread to pick up. If no thread is immediately available, it will create one.
                 Enqueue((threadStart, state, tcs));