urlutil: use the deprecation warning function on the `ui` object

PyCharm flagged this as not existing, and I suspect a copy/paste error.

Differential Revision: https://phab.mercurial-scm.org/D10871

mercurial/utils/urlutil.py

@@ -684,7 +684,7 b' class paths(dict):'
         path to a repo.
         """
         msg = b'getpath is deprecated, use `get_*` functions from urlutil'
-        self.deprecwarn(msg, '6.0')
+        ui.deprecwarn(msg, '6.0')
         # Only fall back to default if no path was requested.
         if name is None:
             if not default: