chore: clean up

Author: MaggieKimani1

src/Microsoft.OpenApi/Models/OpenApiParameter.cs

@@ -1,4 +1,4 @@
-// Copyright (c) Microsoft Corporation. All rights reserved.
+// Copyright (c) Microsoft Corporation. All rights reserved.
 // Licensed under the MIT license.
 
 using System;
@@ -270,7 +270,7 @@ public void SerializeAsV2(IOpenApiWriter writer)
             // deprecated
             writer.WriteProperty(OpenApiConstants.Deprecated, Deprecated, false);
 
-            var extensionsClone = Extensions is not null ? new Dictionary<string, IOpenApiExtension>(Extensions) : null;
+            var extensionsClone = Extensions is not null ? new OpenApiExtensionDictionary(Extensions) : null;
 
             // schema
             WriteRequestBodySchemaForV2(writer, extensionsClone);