Reduce complexity in UselessSetterCall
Reduce complexity in UselessSetterCall

Extract `last_expression` from `on_method_def`.

bbatsov/rubocop,jfelchner/rubocop,alexdowad/rubocop,lumeet/rubocop,backus/rubocop,bbatsov/rubocop,iGEL/rubocop,lucasuyezu/rubocop,mikegee/rubocop,rrosenblum/rubocop,b-t-g/rubocop,vergenzt/rubocop,petehamilton/rubocop,iGEL/rubocop,alexcstark/rubocop,akihiro17/rubocop,panthomakos/rubocop,jmks/rubocop,dreyks/rubocop,melch/rubocop,meganemura/rubocop,vergenzt/rubocop,deivid-rodriguez/rubocop,smakagon/rubocop,rrosenblum/rubocop,alexcstark/rubocop,b-t-g/rubocop,urbanautomaton/rubocop,tdeo/rubocop,melch/rubocop,sue445/rubocop,backus/rubocop,haziqhafizuddin/rubocop,deivid-rodriguez/rubocop,tejasbubane/rubocop,sue445/rubocop,ilansh/rubocop,meganemura/rubocop,tejasbubane/rubocop,lumeet/rubocop,mikegee/rubocop,mclark/rubocop,Drenmi/rubocop,scottmatthewman/rubocop,bankair/rubocop,jfelchner/rubocop,jmks/rubocop,rtlechow/rubocop,NobodysNightmare/rubocop,akihiro17/rubocop,maxjacobson/rubocop,panthomakos/rubocop,urbanautomaton/rubocop,savef/rubocop,smakagon/rubocop,jfelchner/rubocop,mikegee/rubocop,rtlechow/rubocop,jmks/rubocop,bquorning/rubocop,ilansh/rubocop,tdeo/rubocop,maxjacobson/rubocop,tdeo/rubocop,hanumakanthvvn/rubocop,pocke/rubocop,palkan/rubocop,legendetm/rubocop,petehamilton/rubocop,maxjacobson/rubocop,lucasuyezu/rubocop,vergenzt/rubocop,mclark/rubocop,petehamilton/rubocop,alexdowad/rubocop,palkan/rubocop,meganemura/rubocop,tejasbubane/rubocop,hanumakanthvvn/rubocop,dreyks/rubocop,legendetm/rubocop,deivid-rodriguez/rubocop,Drenmi/rubocop,akihiro17/rubocop,palkan/rubocop,haziqhafizuddin/rubocop,sinsoku/rubocop,bquorning/rubocop,bankair/rubocop,pocke/rubocop,rrosenblum/rubocop,bquorning/rubocop,NobodysNightmare/rubocop,savef/rubocop,sinsoku/rubocop,sue445/rubocop,panthomakos/rubocop,scottmatthewman/rubocop