fix of B2pi0pi0 decfile

Supposed to work with Sim10 (priority) AND Sim09. I was a bit quick in committing the previous DecFile and made some cuts "too clever" (in fact the cuts were not perfectly targeting the actual intention, although the effect is rather small). Before the DecFile is actually used somewhere (currently that is not the case) and thus frozen I would like to fix it (and thus avoid clutter): the previous merged version was requiring at least two photons from B2pi0pi0 to fall into the detector acceptance with a significant momentum (the current purpose is to be used as background studies for B2gammagamma). But since merged pi0 can very well be confused with photons it makes much more sense to apply the cuts on the pi0's and not on the subsequent photons. I hope it's still fine to fix the DecFile although it's not an ideal approach I agree.