HARRISBURG - Pennsylvania’s unemployment rate fell slightly in March, as payrolls expanded and every economic sector except for construction recorded growth, according to state figures released Friday.Pennsylvania’s unemployment rate was 7.3%, down a tenth of a percentage point from February’s adjusted rate, the state Department of Labor and Industry said.That was more than a whole point above the national rate of 6% in March.In a survey of households, the labor force remained virtually the same in March, at almost 6.34 million.