TrigValidation: adjust memory requirement of trigger ART tests

Hello,

The memory requirement in panda changed very recently: with --memory we now set the memory per core (2 GB by default), instead of the memory per job. In ART tests that run in multithreaded mode, we typically required # art-athena-mt: 4 and # art-memory: 4096. Before, this would mean 1 GB per core, now this became 4 GB per core. The default of 2 GB per core should guarantee enough memory per job. So I dropped the # art-memory: requirement everywhere, except for test_trigAna_RDOtoRun3DQ_v1Dev_grid which had a very large memory requirement, maybe for some reason. Looking at a recent job, this test consumes marginally more than 2 GB per core, so I set it to 4 GB, to allow for some memory leaks.

I also added the Copyright statement when missing, not sure this was mandatory though.

Adding the 'urgent' label because our ART tests are currently launched on the grid with an excessive memory requirement (e.g. 7 GB per core for some tests), and struggle to find a site where to run.

Cheers, Bertrand