[FIX] sale_timesheet: fix a typo

Someone insisted for a refactoring to land in master.  Because of his
stubborness, a mistake was introduced...  Thank you, mister someone... I
hope that you're happy...

addons/sale_timesheet/static/src/js/timesheet_plan.js

@@ -74,7 +74,7 @@ var ProjectPlan = Widget.extend(ControlPanelMixin, {
 
         return $.when(def1, def2).then(function(){
             self.searchview.do_search();
-            self.update_cp();
+            self._updateControlPanel();
         });
     },