Refs #10090. Added new data file to system test

The system test for PoldiAutoCorrelation works now as well. Some of the checks were a bit too strict, so they were relaxed a bit. The most important check is that the slope is 1 - this stayed as it was.
Refs #10090. Included another file in the analysis

The file was already there from #9711 and actually shows a chopper speed that's a little off.
Merge remote-tracking branch 'origin/feature/10090_correct_poldi_chopper_speed'