[skip-ci] The header of RooChi2Var was not formatted properly (#8531)
[skip-ci] The header of RooChi2Var was not formatted properly (#8531)

* The header of RooChi2Var was not formatted properlly

* some fixes where removed by this PR

* Add \ingroup
olifre/root,olifre/root,olifre/root,olifre/root,olifre/root,olifre/root,olifre/root,olifre/root,olifre/root,olifre/root,olifre/root