Revert "Update BigReactors.cfg"

As Saeldur and Spectralysis mentioned in https://github.com/BevoTechPack/BevoTechPack/pull/562 ,
this config option is simply to allow users to be able to build turbines without having to build inefficient reactors first. Should not affect any cross mod interactions with IC2 blutonium to plutonium or uranium to yellorium.