Allowing enough LHE events for the showering [skip modfiles]

Description of bug

Jobs being broken during production:

https://prodtask-dev.cern.ch/prodtask/inputlist_with_request/61540/ due to 12:38:08 PYTHIA Abort from Pythia::next: reached end of Les Houches Events File

Changes introduced

PowhegConfig.nEvents and evgenConfig.nEventsPerJob were adjusted.

Tests

Issues resolved

See ATLMCPROD-11261 for details.

Closes #