Revert "reverts signature default val for userid in delete_instances(…

…) for now, re #10781"

This reverts commit 00399b8.

make userid default assignment elsewhere until core issue fixed

arches/app/models/graph.py

@@ -564,7 +564,7 @@ def delete(self):
                 )
             )
 
-    def delete_instances(self, userid={}, verbose=False):
+    def delete_instances(self, userid=None, verbose=False):
         """
         deletes all associated resource instances