Fix cancel action on deletion confirmation form Currently crashed with RequestError: invalid action '__action_cancel'. It's broken as of https://hg.logilab.org/master/cubicweb/rev/cb217b2b3 This fix is similar as the one done in https://hg.logilab.org/master/cubicweb/rev/9f1c89e7426d Closes #13521493

"""cubicweb-%(cubename)s application package

%(longdesc)s
"""