Use Threa.Sleep instead of SpinWait

Author: mdaigle

src/Microsoft.Data.SqlClient/tests/UnitTests/ConnectionPool/ChannelDbConnectionPoolTest.cs

@@ -346,7 +346,7 @@ out DbConnectionInternal? failedConnection
             secondTaskReady.Wait();
 
             // Use SpinWait to ensure both tasks are actually waiting
-            SpinWait.SpinUntil(() => false, 100);
+            Thread.Sleep(100);
 
             // Start both requests
             startRequests.Set();