Remove "number of node" positional option

src/main.cpp

@@ -41,7 +41,7 @@ int main(int argc, char *argv[])
   {
     CLI::App app{"Pastis help"};
 
-    app.add_option("number,-n,--number", number, "Number of cells");//->required();
+    app.add_option("-n,--number", number, "Number of cells");//->required();
 
     app.add_option("filename,-f,--filename", filename, "gmsh file");//->required();