Remove redundant using directive in C# template

Author: Fellmonkey

templates/cli/lib/type-generation/languages/csharp.js.twig

@@ -54,11 +54,7 @@ using System;
 using System.Collections.Generic;
 using System.Linq;
 using System.Text.Json.Serialization;
-<% for (const attribute of collection.attributes) { -%>
-<% if (attribute.type === 'relationship') { -%>
-using Appwrite.Models;
-<% } -%>
-<% } %>
+
 namespace Appwrite.Models
 {
 <% for (const attribute of collection.attributes) { -%>