Removed not used keys

htdocs/langs/en_US/bills.lang

@@ -8,7 +8,6 @@ BillsCustomersUnpaid=Unpaid customer's invoices
 BillsCustomersUnpaidForCompany=Unpaid customer's invoices for %s
 BillsSuppliersUnpaid=Unpaid supplier's invoices
 BillsSuppliersUnpaidForCompany=Unpaid supplier's invoices for %s
-BillsUnpaid=Unpaid
 BillsLate=Late payments
 BillsStatistics=Customer's invoices statistics
 BillsStatisticsSuppliers=Supplier's invoices statistics
@@ -217,7 +216,6 @@ DateEcheance=Due date limit
 DateInvoice=Invoice date
 NoInvoice=No invoice
 ClassifyBill=Classify invoice
-NoSupplierBillsUnpaid=No suppliers invoices unpaid
 SupplierBillsToPay=Suppliers invoices to pay
 CustomerBillsUnpaid=Unpaid customers invoices
 DispenseMontantLettres=The bill drafted by mechanographical are exempt from the order in letters