Fix schema services dispose handling.

Author: michaelstaib

src/HotChocolate/Core/src/Execution/RequestExecutorResolver.cs

@@ -471,7 +471,7 @@ public RegisteredExecutor(
 
         public void Dispose()
         {
-            if (_disposed)
+            if (!_disposed)
             {
                 if (Services is IDisposable d)
                 {