s/ moar_jit / moar_nojit /

moar now defaults to jit, so use --backends=moar for jit and --backends=moar-nojit for without jit

https://github.com/coke/perl6-roast-data/blob/135314ee4e46a110d512959e7a3d4eb54bf5a8f7/bin/rakudo.moar.sh#L12