Fix: a bug in gg. 2 options were using the same option name (-p)

tools/graphgen/graphGen_arg.ml

@@ -241,7 +241,7 @@ let (mkoptab : string array -> t -> unit) =
       [(["Set the second radius around all nodes.";
          "2 by default.\n"],"QUDG")];
 
-    mkopt args ["--probability";"-p"]~arg:" <float>"
+    mkopt args ["--probability"]~arg:" <float>"
       (Arg.Float (fun p -> args.qudg.p <- p))
       [(["Sets the probability of the nodes being neighbors when they are ";
            "inside the second";