[RF][Docs] Document constructor of RooAbsOptTestStatistic.
[RF][Docs] Document constructor of RooAbsOptTestStatistic.

root-mirror/root,root-mirror/root,olifre/root,olifre/root,root-mirror/root,olifre/root,olifre/root,root-mirror/root,root-mirror/root,root-mirror/root,root-mirror/root,olifre/root,olifre/root,root-mirror/root,olifre/root,olifre/root,root-mirror/root,olifre/root,root-mirror/root,root-mirror/root,olifre/root,olifre/root