Remove unnecessary parenthesis in cron documentation

Closes #13502
(grafted from 82d409471f4af739c2faa412af291ac72e8e0e43)

--HG--
branch : 7.0

trytond/doc/topics/cron.rst

@@ -19,9 +19,9 @@ and the interval of time between calls. The method must be a class method of a
 To register a new method with the scheduler, you must extend the ``ir.cron``
 model and append the new method to the
 :attr:`~trytond.model.fields.Selection.selection` attribute of the ``method``
-field in :meth:`~trytond.model.Model.__setup__()`. The name of the selection
-must be the model name and the method name joined together with a ``|`` between
-them.
+field in :meth:`~trytond.model.Model.__setup__`.
+The name of the selection must be the model name and the method name joined
+together with a ``|`` between them.
 
 Example: