PowhegControl: adding mass_rwg_frac parameter in gg4l process - AGENE-2207
requested to merge atlas-physics/pmg/mcexperts/powheg-experts/athena:master-Powheg-AddParameterIngg4l into master
This MR is adding a new parameter to the gg4l process. More details in the AGENE-2207 JIRA ticket.
(putting alsoTargeting:21.6 label for completeness, but it's not particularly needed)