Use t2.medium instead of t2.micro in create-ec20leader.sh
Use t2.medium instead of t2.micro in create-ec20leader.sh

Hopefully fixes memory error coming out of newer toil versions on some large inputs
vgteam/toil-vg,vgteam/toil-vg,glennhickey/toil-vg,glennhickey/toil-vg