Address mc21 pileup re-weight issue

Address issue with pileup re-weight for mc21 affecting electrons and muons. For mc21 use the following PRW files in Event.py:

/eos/user/h/hrussell/AMG_Data/mc21a.410000.physlite.prw.root
/eos/user/h/hrussell/AMG_Data/fakedata_mc21a_MCMuProfile.lumicalc.422633.root

located in /afs/cern.ch/user/s/schaarsc/public/for_TJ

More info: https://its.cern.ch/jira/browse/ATLASG-1628?focusedCommentId=4297949&page=com.atlassian.jira.plugin.system.issuetabpanels%3Acomment-tabpanel