Remove non-existent Attributes reference

Author: acupofjose

Functions/Client.cs

@@ -1,15 +1,11 @@
 using Newtonsoft.Json;
-using Supabase.Functions.Attributes;
 using Supabase.Functions.Responses;
 using System;
 using System.Collections.Generic;
-using System.Diagnostics;
 using System.Net.Http;
 using System.Text;
-using System.Threading;
 using System.Threading.Tasks;
 using System.Web;
-using static Supabase.Functions.Client;
 
 namespace Supabase.Functions
 {