Reduce number of events in some ART tests
These tests take ~24 hours and sometimes don't finish in a day so we don't get results copied back. This MR halves the number of events in each test.
modified: Trigger/TrigValidation/TrigAnalysisTest/test/test_trigAna_RDOtoRDOTrig_grid.py modified: Trigger/TrigValidation/TrigAnalysisTest/test/test_trigAna_q221_RDOtoAOD_mt1_grid.sh