Fix: Translation

htdocs/langs/en_US/bills.lang

@@ -167,9 +167,9 @@ ConfirmCustomerPayment=Do you confirm this payment input for <b>%s</b> %s ?
 ConfirmValidatePayment=Are you sure you want to validate this payment ? No change can be made once payment is validated.
 ValidateBill=Validate invoice
 NumberOfBills=Nb of invoices
-NumberOfBillsByMonthHT=Nb of invoices by month (net of tax)
+NumberOfBillsByMonth=Nb of invoices by month
 AmountOfBills=Amount of invoices
-AmountOfBillsByMonth=Amount of invoices by month
+AmountOfBillsByMonthHT=Amount of invoices by month (net of tax)
 ShowSocialContribution=Show social contribution
 ShowBill=Show invoice
 ShowInvoice=Show invoice