Drop NANO step from upgrade combined premixing workflow

NANO is configured to use step3_inMINIAODSIM.root input file, but in
combined premixing workflow the file is step4_inMINIAODSIM.root.
Simplest option is to just drop the NANO step from these workflows.

Configuration/PyReleaseValidation/python/relval_upgrade.py

@@ -132,6 +132,6 @@ def makeStepName(key,frag,step,suffix):
                                                       [slist[0]] +                      # Start with signal generation
                                                       stepList['Premix'] +              # Premixing stage1
                                                       [slist[1].replace("PUPRMX", "PUPRMXCombined")] + # Premixing stage2, customized for the combined (defined in relval_steps.py)
-                                                      slist[2:]]                        # Remaining standard steps
+                                                      filter(lambda x: "nano" not in x.lower(), slist[2:])]    # Remaining standard steps (excluding NANOAOD because of input file numbering mismatch)
 
             numWF+=1