[RF] Fix function signature of operator<<() in RooAbsArg.cxx
[RF] Fix function signature of operator<<() in RooAbsArg.cxx

olifre/root,olifre/root,olifre/root,olifre/root,olifre/root,olifre/root,olifre/root,olifre/root,olifre/root,olifre/root,olifre/root