Deep tagger fixes
- use combined ZHbbvsQCD discriminator for decorrelated DeepAK8 (Z, H look very similar after mass decorrelation)
- simplify setup and code
- fix bug where low-pT AK8 jets weren't actually removed
The last item caused the estimate of processing time in #361 to be unnecessarily pessimistic. The actual change is 9.7 ev/s to 9.3 ev/s.