Remove redundant using

Remove redundant using statement.

Author: martincostello

src/TodoApp/OpenApi/AspNetCore/AspNetCoreOpenApiEndpoints.cs

@@ -1,7 +1,6 @@
 // Copyright (c) Martin Costello, 2024. All rights reserved.
 // Licensed under the Apache 2.0 license. See the LICENSE file in the project root for full license information.
 
-using Microsoft.AspNetCore.OpenApi;
 using Microsoft.OpenApi.Models;
 
 namespace TodoApp.OpenApi.AspNetCore;