Remove unnecessary usings.

BulkPrintingAPI/Controllers/VendorsController.cs

-using System;
-using System.Collections.Generic;
-using System.Data.SqlClient;
-using System.Linq;
-using System.Threading.Tasks;
-using Microsoft.AspNetCore.Http;
+using MAX.Models;
 using Microsoft.AspNetCore.Mvc;
 using Microsoft.EntityFrameworkCore;
-using MAX.Models;
+using System.Threading.Tasks;
 
 namespace BulkPrintingAPI.Controllers
 {