Use `ROOT` function `TLorentzVector::DeltaPhi()` instead of own implementation

[HerrHorizontal]

It might be more convenient to use the ROOT function TLorentzVector::DeltaPhi() instead, if possible in

Excalibur/Compile/interface/ZJetProduct.h

Line 391 in 82f6c70

jnpf += GetTransverseAngleCosine(&jet->p4, &m_z.p4);

. For example:

jnpf += cos( jet->p4.DeltaPhi(&m_z.p4) );

Not sure though, if this is posible due to the various abstraction layers.

Originally posted by @HerrHorizontal in #60 (comment)