Run.set_tags won't accept string, irrespective of documentation

[oliverw1]

In at least versions 1.22.0 and 1.28.0, the documentation for tagging runs states that one can pass a string, like run.set_tags("foo"). However, since RunHistoryFacade.set_tagscalls WorkspaceClient._sanitize_tags, this will fail, as the latter calls the method items on its argument.