Modified the output file name for DigitizationTest test_Digi_tf_mc16a_ttbar_algs.sh (ATLASSIM-5349)

test_Digi_tf_mc16a_ttbar_algs.sh is comparing to the wrong reference set and the script need to change the output file name to art-output: mc16a_ttbar_algs.RDO.pool.root to differentiate it from the output from test_Digi_tf_mc16a_ttbar.sh

FYI: @jchapman @abasalae, @tadej, @mduehrss (ATLASSIM-5349)