Changing input collection for tauGenJets in miniAOD

In the default PAT, the tauGenJets are made from genParticles. The miniAOD does not contain genParticles, so the links stored in pat::Tau are broken. The prunedGenParticles contain all particles necessary for tauGenJet building and are contained in miniAOD.

Physics output impact: none expected (however the links genJet constituents will work in miniAOD)

Timing impact: might be slightly faster (using smaller collection for tauGenJet production)
Output size impact: none expected (the references were filled also before, only they were pointing to non-existing objects)

@mbluj @gpetruc @arizzi

Can be forward-ported to 71x and 72x