Remove unused using statement

Jellyfin.Api/Controllers/LibraryController.cs

@@ -11,7 +11,6 @@ using System.Threading.Tasks;
 using Jellyfin.Api.Attributes;
 using Jellyfin.Api.Constants;
 using Jellyfin.Api.Extensions;
-using Jellyfin.Api.Helpers;
 using Jellyfin.Api.ModelBinders;
 using Jellyfin.Api.Models.LibraryDtos;
 using Jellyfin.Data.Entities;