Adjust number of events for Run 4 ttbar PU0 IDPVM ART tests
Run 4 sim+reco ttbar PU0 IDPVM ART test takes several days to run and often ends up crashing. No equivalent test is actually run for Run 3 (sim+reco tests are only run for single particles). Reducing the number of events processed to 1k instead of 10k to check if it's more manageable.