erp5_payroll_l10n_fr: sometimes CTP amount is negative

In the case the CTP is for a refund

bt5/erp5_payroll_l10n_fr/SkinTemplateItem/portal_skins/erp5_payroll_l10n_fr/DSNMonthlyReport_getDataDict.py

@@ -202,7 +202,10 @@ if block_id == 'S21.G00.23':
   rubric_value_dict['S21.G00.23.002'] = target['cap']
   rubric_value_dict['S21.G00.23.003'] = ('' if not target['rate'] else formatFloat(target['rate']))
   if target['quantity']:
+    if target['code'][:3] != '801':
       assert target['quantity'] > 0
+    else:
+      assert target['quantity'] < 0
     rubric_value_dict['S21.G00.23.005'] = formatFloat(round(target['quantity']))
   else:
     rubric_value_dict['S21.G00.23.004'] = formatFloat(round(target['base']))