This MR hopefully fixes the CaloClusterThinning for taus, to thin simultaneously the non-origin-corrected and origin-corrected topocluster collections.
It is fully based on the JetCaloClusterThinning implementation from late 2017, when this had been fixed for jets.
Now, derivations willing to thin tau clusters should specify
TopoClCollectionSGKey = "LCOriginTopoClusters" and
AdditionalTopoClCollectionSGKey = ["CaloCalTopoClusters"].
The cone size is 0.2 if not set by the user, as originally intended.
Minor other modification: one deprecated variable no longer used in R21 has been dropped from the smart slimming list.