Remove old button_draft rpc declaration

forecast.py

@@ -55,9 +55,6 @@ class Forecast(Workflow, ModelSQL, ModelView):
 
     def __init__(self):
         super(Forecast, self).__init__()
-        self._rpc.update({
-            'button_draft': True,
-        })
         self._sql_constraints += [
             ('check_from_to_date',
              'CHECK(to_date >= from_date)',