Fix electron GSF sequence for fastsim HLT (72X)

Fix for the gsfElectron sequence in FastSim HLT, that showed up since the migration to gsf tracking for electrons. 

@matteosan1 @VinInn @beaudett

@lveldere: I let you push this one for the next 72X release for next week's MWGR9 if you think so. (This is not needed for any MWGR, of course, but it can be a good opportunity for having it in).