update bbyy mc20 sample cross section value
update cross section value for mc20 sample used in post-processing. the updated values take into account cross section, branching ratio and generator filter efficiency
xs and br reference: ggF HH https://twiki.cern.ch/twiki/bin/view/LHCPhysics/LHCHWGHH?redirectedfrom=LHCPhysics.LHCHXSWGHH VBF HH https://twiki.cern.ch/twiki/bin/view/AtlasProtected/DiHiggsCombination#Signal_normalisation_and_Higgs_B single H https://twiki.cern.ch/twiki/bin/view/LHCPhysics/CERNYellowReportPageAt13TeV BR https://twiki.cern.ch/twiki/bin/view/LHCPhysics/CERNYellowReportPageBR#Higgs_2_gauge_bosons