Remove unused function to calculate track parameters in Pantau
As part of pantau cleanup package, remove unused function to calculate track impact parameters.
Tested using 1000 events from Ztautau RDO and rerunning the tau reconstruction using:
https://gitlab.cern.ch/atlas/athena/-/blob/main/Reconstruction/tauRec/python/TauConfig.py
Using "diffPool" and "diff-root" to look at the difference between AOD reference and new AOD produced with the updates in this MR and no differences spotted by the scripts