ui_test: ignore errors with cell/getId for testAccessUnauthorizedRelationValue
This listbox can be used to show documents that user is not allowed to access, so this `cell/getId` can raise. In Zope2 it was raising Unauthorized and this Unauthorized was catched, on Zope4 it is raising NotFound, which is no longer catch since 850e436e ( Products.ERP5Form.Form: Let NotFound exceptions propagate during rendering, 2022-11-25), so this NotFound was raised as a site error, which caused an error in the test.