Fix comparisons in test_Digi_tf_mc20e_MP_reproducibility.sh (ATLASSIM-6586)

Add missing RDOMerge_tf.py step for test_Digi_tf_mc20e_MP_reproducibility.sh ART job (ATLASSIM-6586)

Also clean-up configuration for RUN4 reproducibility ART jobs - don't expect this to fix the failing diff-root checks. Most likely this will require the inputs to be updated.

Also fix the logic for setting the return code in test_Digi_tf_mc20e_MP_presampling_reproducibility.sh