Update ART Digitization tests to new conditions

After !56073 (merged) which removed hardwired NSW conditions from the configuration files was merged, ART digitization tests failed as the global conditions tag used there OFLCOND-MC21-SDR-RUN3-05 does not contain /MDT/MM/CHARGE/SIDEA (and possibly other) folder. This was error was also seen during the development of !56073 (merged) and fixed by updating the conditions to OFLCOND-MC21-SDR-RUN3-07 (which is the one used in mc21a anyway). This MR also updates the conditions tag in the ART tests.

Keeping as Draft until somebody has a look and confirms I did it ok, since I am not that fluent in ART, but it's actually quite urgent as we want to build a release for physics validations of the new conditions as a preparation of fast reprocessing.

cheers, Tommaso