Berger & Montague, the Center City law firm, said Friday that it had settled a whistle-blower lawsuit against pharmaceutical giant Genzyme Corp. for a total of $5.9 million. The suit, brought under the False Claims Act, alleged that Genzyme had effectively understated sales of its medications to drug wholesalers. That in turn resulted in reduced rebate payments to state Medicaid programs, which must obtain the lowest available prices from pharmaceutical manufacturers.