Remove unused UseNSWMode property from MuonSegmentFinderAlg

Hi,

this MR removes the UseNSWMode property from the MuonSegmentFinderAlg which is never used anywhere.

FYI: I did on purpose not replace MuonIdHelperTool by MuonIdHelperSvc since I want to sweep this change into 21.3 and 21.9 without conflicts.

Best, Nico