Update PLOTTING_ATLAS_Z_TOT_13TEV.yaml
This fixes a wrong label for the ATLAS_Z_TOT_13TEV
data set, which was misclassified as DY_CC, while it must be DY_NC.
This fixes a wrong label for the ATLAS_Z_TOT_13TEV
data set, which was misclassified as DY_CC, while it must be DY_NC.