Removing incorrect using.

--HG--
branch : dev

src/Orchard/Data/SessionFactoryHolder.cs

@@ -1,6 +1,5 @@
 using System;
 using System.IO;
-using System.Runtime.Serialization.Formatters.Soap;
 using System.Xml.Serialization;
 using NHibernate;
 using NHibernate.Cfg;