[sobject] fix notification operation
regression introduced in bf4003760e02 Operation use self. session. not self._cw.
I'm a bit surprised that its not tested.
closes ##2870077
Latest changes
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* table of `all latest changes`_
Links below is providing useful RQL query example.
.. _all latest changes: view?rql=Any+M%2CX+WHERE+X+modification_date+M+ORDERBY+M+DESC+LIMIT+30