TrigInDetValidation: fix comparitor.json

Hello,

This MR removes a comma in a json file (only used by ART trigger ID tests) which causes a parsing error (ATR-30689).

Note: after the fix, another error shows up due to the removal of tau legacy chains (ATR-30696)

RuntimeError: Request to enable/disable chain HLT_mu24_ivarmedium_tau25_idperf_tracktwoMVA_probe_03dRAB_L1MU14FCH that is not in menu

Tagging @sutt and @bkerridg .

Cheers, Bertrand