Including module necessary for standalone PFTau execution

TransientTrackBuilderESProducer is necessary for the tau reconstruction. When PFTau is executed during RECO sequence, it is already loaded. Also this module is loaded with patCandidates_cff.py. However, when trying to execute PFTau only without loading the full PAT creating config, the code crashed due to this missing module.

This PR should allow simple and more intuitive re-running of PFTau. It should have no effect neither on timing or output content or size.