Add pragmas to DisplayPreferences migration files

Jellyfin.Server.Implementations/Migrations/20200717233541_AddDisplayPreferences.Designer.cs

@@ -1,4 +1,6 @@
-// <auto-generated />
+#pragma warning disable CS1591
+
+// <auto-generated />
 using System;
 using Jellyfin.Server.Implementations;
 using Microsoft.EntityFrameworkCore;

Jellyfin.Server.Implementations/Migrations/20200717233541_AddDisplayPreferences.cs

@@ -1,4 +1,7 @@
-using System;
+#pragma warning disable CS1591
+#pragma warning disable SA1601
+
+using System;
 using Microsoft.EntityFrameworkCore.Migrations;
 
 namespace Jellyfin.Server.Implementations.Migrations