Comment out Pythia8 function

Comment out the Pythia8 function to disable it.

Author: dsekihat

MC/config/PWGEM/ini/tests/pythia8_OO_536_VM2ll.C

@@ -2,7 +2,7 @@ int External() {
     return 0;
 }
 
-int Pythia8()  
-{  
-  return External();  
-} 
+//int Pythia8()  
+//{  
+//    return External();
+//}