fix broken helm download command in instructions, again
fix broken helm download command in instructions, again

fission/fission,life1347/fission,platform9/fission,fission/fission,platform9/fission,life1347/fission,life1347/fission,fission/fission,fission/fission,life1347/fission,life1347/fission,life1347/fission,platform9/fission,life1347/fission,platform9/fission,life1347/fission,life1347/fission