add stats-extension of extended Z' sample to default grid file list

This MR adds the increase in events for the extended Z' mc20d sample to the grid submission file list.

Note: Don't be confused by the different s-tag, it originates because the "original" mc20d extended Z' sample was re-simulated from mc16 events and now that new events have been generated, a different s-tag was used. The two samples are intended to be used together and can be merged as part of the preprocessing.