Change version of frozen showers to MC23
Following the successful validation of https://its.cern.ch/jira/browse/ATLPHYSVAL-900, this changes the version of frozen showers from MC21_v2 to MC23_v1. I have also removed the non-existing file LArG4ShowerLib.FCAL1.211.root from the list of files.
I ran the CI tests locally and the simulation went fine, then failing as expected in the comparison with the reference. I expect the same will happen in the CI test here. If everything is expected, I will update the reference next.
Tommaso