Remove variables availability check in MuonSelectorToolsTester

This MR removes some lines from MuonSelectorToolsTester. These lines check the availability of certain variables used in the muon selection, and prints a message if they are missing. They can cause a crash in rare circumstances, if the primary track pointer of the muon is a null pointer. Rather than implementing a null pointer test, I prefer to remove the lines because the list of variables checked is not exhaustive of all variables used in the muon selection. There is no point in fixing this and spending effort on keeping this part up to date, because the MuonSelectionTool itself prints a warning for any missing variables, which will show up in any case when running the tester.