This group of “Gold Rush” miners is like none of their predecessors on the top-rated Discovery series.“Gold Rush” returns Friday for Season 11 with a two-hour episode (8-10 p.m.) and a new mining boss: Fred Lewis, a former special forces medical sergeant and linguist who’s assembled a team of five veteran pals to dig for gold in a ghost town near Sumpter, Ore.“They’ve all overcome obstacles,” says Lewis, 42, who took a bullet to the helmet in Afghanistan.