Improves changelog

Author: alex-kulakov

ChangeLog/6.0.4_Z_Final.txt

@@ -1,4 +1,5 @@
 [main] Session.SelectStorageNode() marked as obsolete
+[main] Removed obsolete static Session.Open() methods
 [main] Domain.OpenSessionAsync() methods can only open a session to default storage node now
 [main] Introduced StorageNode.OpenSession() and StorageNode.OpenSessionAsync() method sets to open sessions to the node
 [main] Fixed issue when DirectPersistentAccessor.SetReferenceKey() was unable to set reference for saved Entities