Update Jellyfin.Server/Middleware/QueryStringDecodingMiddleware.cs

Co-authored-by: Claus Vium <cvium@users.noreply.github.com>

Jellyfin.Server/Middleware/QueryStringDecodingMiddleware.cs

@@ -1,4 +1,3 @@
-using System;
 using System.Threading.Tasks;
 using Microsoft.AspNetCore.Http;
 using Microsoft.AspNetCore.Http.Features;