Remove error message if files from dev area loaded

Hi @akraszna,

in the MuonPerformanceAnalysis we've introduced now the pile-up reweighting during n-tuple production since the run-II data-taking is over. In order not to maintain our own config files, we'd like to rely on the central files maintained by the SUSY group. The problem is that the PathResolver is prompting an Error message in AthDerivation making our jobs to fail on the grid.

I've removed the ifdef flag in this MR such that we can also use the central pile-up and cross-section files from AthDerivation

Tagging: @fsforza, @szambito, @egramsta, @guirriec, @boeriu, @krumnack, @nkoehler