Changing tt FCNC jO to use PWHG LHE reader

Description of bug

In the discussion in ATLMCPROD-10646 it was suggested to use the POWHEG LHE reader in the job option settings of the PH7 ttbar FCNC in top decay DSIDs 602063-602066. Since the job options were already merged, this bug fix merge request is needed. No events have been generated with these job options so far.

Changes introduced

Changing the input parameter usepwhglhereader=False to usepwhglhereader=True in the Herwig7Config.lhef_powhegbox_commands call. In the DSID directories 602064-602066 a symlink to the changed PowhegControl_ttFCNC_NLO.py file in the DSID directory 602063 is used, such that this change effects the job options of all four DSIDs.

Tests

Events were privately generated for the PH7 ttbar sample with t > u H decay and checked that the different usepwhglhereader setting did not change the simulation result.

Issues resolved

Correct POWHEG LHE reader usage

Closes #