Swap qqx bool superfluous, calculation takes place in QMRK limit. Momenta needs to be entered intended manner: - p2 in James Cockburn's Thesis corresponds to quark. - p3 in James COckburn's Thesis corresponds to anti-quark.

The lack of a W emitted from the vertex gives some freedom (as the extra -1 it would add to phases due to quark propagators does not exist), and allows us to make the call to this function without reversing the momenta. Note, this fix ensures that reversing momenta and types as per the reverse_ME test inside of test_ME_generic does not fail, and yet no changes to any ME values for the PSPs probed in t/4j.lhe.gz were necessary.

Related Issues:

• Relates to https://gitlab.dur.scotgrid.ac.uk/hej/HEJ/issues/113
• Specifically task 3.