cleanup usings

Author: MaggieKimani1

src/Microsoft.OpenApi.OData.Reader/EdmModelOpenApiExtensions.cs

@@ -1,9 +1,8 @@
-// ------------------------------------------------------------
+// ------------------------------------------------------------
 //  Copyright (c) Microsoft Corporation.  All rights reserved.
 //  Licensed under the MIT License (MIT). See LICENSE in the repo root for license information.
 // ------------------------------------------------------------
 
-using System.Collections.Generic;
 using Microsoft.OData.Edm;
 using Microsoft.OData.Edm.Validation;
 using Microsoft.OpenApi.Any;