Added cut to remove the first data point of the ATLAS W+jet pT measur…

This PR implements a cut on the pT distribution for the ATLAS W+jet measurement. The cut removes two data points (one for W+ and one for W-) at the smallest pT, where resummation effects may be large. Note that here the K-factor is indeed ~30% for these points. Although this data sets has been fitted for quite some time now - and the cut won't possibly change anything - I believe that it's neater to have it.