clean up: remove unused namespaces

Disco.Services/Devices/Exporting/DeviceExport.cs

@@ -11,7 +11,6 @@ using System.Collections.Generic;
 using System.ComponentModel.DataAnnotations;
 using System.Data;
 using System.Data.Entity;
-using System.IO;
 using System.Linq;
 
 namespace Disco.Services.Devices.Exporting

Disco.Services/Devices/Importing/Fields/DeviceDecommissionedDateImportField.cs

@@ -6,7 +6,6 @@ using Disco.Services.Logging;
 using System;
 using System.Collections.Generic;
 using System.Data;
-using System.Data.Entity;
 using System.Globalization;
 using System.Linq;