ST. LOUIS — The effort to build a new riverfront football stadium in St. Louis got a big boost Monday when a judge ruled that approval from city voters is not necessary to use city tax money for the project.St. Louis Circuit Judge Tomas Frawley’s ruling voided a city ordinance requiring voter approval for any project using tax dollars for a professional sports facility.He called the 2002 law’s language confusing and vague.He also ruled that the stadium plan does not break a state law requiring it to be …