Fix syntax in DigitizationPUConfigNew_test.py (ATLASSIM-5031)
Replace ConfigFlags.Digitization.PU.RunAndLumiOverrideList
with ConfigFlags.Input.RunAndLumiOverrideList
in DigitizationPUConfigNew_test.py
Fixes bug introduced in !37867 (merged) - see ATLASSIM-5031