Fix to R(D+)-analysis decfiles for Sim10 onwards

Corrected a functor used in the generator-level cuts of the decfiles associated to the R(D+) analysis, as well as a minor fix in the decay descriptors. The correction should be applied from Sim10 onwards, keeping the same number for the decfiles (as discussed in https://its.cern.ch/jira/browse/LHCBGAUSS-2288).