Fix configuration error for the FTF L2ResidualCalculator

The wrong tool variable was being set by the job option for the TrigL2ResidualCalculator
in the FastTrackFinder, resulting in the ZFinder configuration being given the wrong
configuration, which caused a crash in the python3 execution reported in  https://its.cern.ch/jira/browse/ATR-21463.

This fixes https://its.cern.ch/jira/browse/ATR-21463