Fix broken Revit test case

The regression is caused by my recent change to remove ``String.FromObject`` and ``ToString()``  built-in function. 

For these two regressions, one is when migrating from old node, old GUID was not used, therefore Dynamo failed to create connector (based on start/end GUID). The fix is to reuse old GUID.

The other regression is because of using ``String.FromObject`` node, which is marked as obsolete. Update .dyn file to use ``String from Object`` node.