Follow-up from "Add HltEfficiencyChecker tool to mooreanalysis" - check behaviour of --dump

The following discussion from !1 (merged) should be addressed:

• @dovombru started a discussion: (+2 comments)

  While testing the scripts here, I noticed that the instructions in the MR here are not up to date. The command documented in HltEfficiencyChecker.py works though. Maybe make clear that the --dump option also needs the other arguments as input to work.