Revert "Use default TRT active gas in geo model unless in simulation."

This reverts merge request !58578 (merged) , basically due to a mix-up of the two configs styles/

ping @jchapman and @cgrefe

we will need one with the flags placed in the respective config styles ...

if not DetFlags.simulate.TRT_on():
     trtDetectorTool.DoXenonArgonMixture = False
     trtDetectorTool.DoKryptonMixture = False

for old in this file.

and the reverted code

from AthenaConfiguration.Enums import Project, ProductionStep
from AthenaConfiguration.AllConfigFlags import ConfigFlags
if ConfigFlags.Common.Project is not Project.AthSimulation and ConfigFlags.Common.ProductionStep is not ProductionStep.Simulation:
    trtDetectorTool.DoXenonArgonMixture = False
    trtDetectorTool.DoKryptonMixture = False

should go to https://gitlab.cern.ch/atlas/athena/-/blob/master/InnerDetector/InDetDetDescr/TRT_GeoModel/python/TRT_GeoModelConfig.py#L5