Remove unused namespaces

Author: Warren Buckley

src/Umbraco.Forms.Extensions.Crm.Hubspot/HubspotController.cs

@@ -1,10 +1,7 @@
 using Newtonsoft.Json;
-using Newtonsoft.Json.Linq;
 using System;
 using System.Collections.Generic;
-using System.Linq;
 using System.Net.Http;
-using System.Net.Http.Json;
 using Umbraco.Core.Composing;
 using Umbraco.Core.Logging;
 using Umbraco.Web.Editors;