[FIX] hr_timesheet_invoice: Call super on on_change_account_id of hr.analytic.timesheet

`hr_timesheet_invoice.py` overrides `on_change_account_id`
of model `hr.analytic.timesheet`.

The super call wasn't done, probably because this on_change
method in the base model was trivial:
`return {'value':{}}`

Nevertheless, if another module overrides this on_change,
according to the module dependences,
this method could have been called first in the calling chain,
discarding the changes from the other overriden
`on_change_account_id` methods, preventing
any customization in this on_change according to the
current database state.

Closes #8248

addons/hr_timesheet_invoice/hr_timesheet_invoice.py

@@ -320,7 +320,8 @@ class account_analytic_line(osv.osv):
 class hr_analytic_timesheet(osv.osv):
     _inherit = "hr.analytic.timesheet"
     def on_change_account_id(self, cr, uid, ids, account_id, user_id=False):
-        res = {}
+        res = super(hr_analytic_timesheet, self).on_change_account_id(
+            cr, uid, ids, account_id, user_id=user_id)
         if not account_id:
             return res
         res.setdefault('value',{})