Fix node aliases with trailing underscores

[jacobtylerwalls]

5 nodes have aliases with trailing underscores, making them unable to be usefully queried as part of the Arches Model QuerySets feature. (Related: I should add some error handling around that.)

In [10]: Node.objects.filter(alias__endswith="_", graph__source_identifier=None).values_list('alias', flat=True)
Out[10]: <QuerySet ['concept_', 'creation_sources_', 'data_assignment_', 'professional_activity_identifier_data_assignment_', 'standards_sources_']>

Suggest we fix the models.