Fix typo in TaylorVar/power.
Fix typo in TaylorVar/power.

Previously TaylorVar/power only allowed for scalar powers of TaylorVars. Now we
should be able to do elementwise constant powers.

edowson/drake,astrorog/drake,manuelli/drake,crogers3/drake,tkoolen/drake,sheim/drake,edowson/drake,psiorx/drake,crogers3/drake,sheim/drake,sheim/drake,thientu/drake,hanssusilo/drake,crogers3/drake,thientu/drake,crogers3/drake,scottviteri/drake,thientu/drake,hanssusilo/drake,thientu/drake,billhoffman/drake,crogers3/drake,tkoolen/drake,tkoolen/drake,billhoffman/drake,scottviteri/drake,astrorog/drake,edowson/drake,thientu/drake,psiorx/drake,manuelli/drake,manuelli/drake,psiorx/drake,billhoffman/drake,scottviteri/drake,psiorx/drake,astrorog/drake,hanssusilo/drake,manuelli/drake,tkoolen/drake,billhoffman/drake,tkoolen/drake,edowson/drake,tkoolen/drake,sheim/drake,manuelli/drake,billhoffman/drake,astrorog/drake,crogers3/drake,hanssusilo/drake,psiorx/drake,astrorog/drake,hanssusilo/drake,crogers3/drake,edowson/drake,manuelli/drake,scottviteri/drake,thientu/drake,edowson/drake,edowson/drake,billhoffman/drake,edowson/drake,psiorx/drake,billhoffman/drake,crogers3/drake,scottviteri/drake,psiorx/drake,tkoolen/drake,hanssusilo/drake,scottviteri/drake,hanssusilo/drake,thientu/drake,sheim/drake,manuelli/drake,astrorog/drake,hanssusilo/drake,sheim/drake,astrorog/drake,billhoffman/drake,sheim/drake,sheim/drake,scottviteri/drake,psiorx/drake