Properly dispose dbContext in MigrateUserDb

Jellyfin.Server/Migrations/Routines/MigrateUserDb.cs

@@ -67,7 +67,7 @@ namespace Jellyfin.Server.Migrations.Routines
             using (var connection = new SqliteConnection($"Filename={Path.Combine(dataPath, DbFilename)}"))
             {
                 connection.Open();
-                var dbContext = _provider.CreateDbContext();
+                using var dbContext = _provider.CreateDbContext();
 
                 var queryResult = connection.Query("SELECT * FROM LocalUsersv2");