SPRINGFIELD — Another federal conviction for political corruption in Illinois, another call for tougher ethics laws.A jury last week slapped convictions on four political insiders in a wide-ranging case involving power giant ComEd’s bribery of the once-powerful speaker of the Illinois House.While a key House Democrat confirmed Tuesday that discussions about a package of ethical tune-ups were underway, former Gov. Pat Quinn, who has made a career of chasing government reform, delivered a letter to Democratic …