It seems in some cases when saving a BDT model trained with lightgbm
sigmoid:1 is added to the line which specify the objective. This seems to be a newest feature. This is the default for binary classification, so nothing really to be changed and the additional information can be discarded.
This MR just change a script to convert the output of lightgbm to ROOT files used by ATLAS. It doesn't change anything connected to reconstruction.
This should be propagated to rel 22.0 and 21.2
This closes ATLASRECTS-7035