Fix unused argument warning

Change-Id: Iad1aa1532ce743a437a4b120de09266d936e14e1

Rendering/Matplotlib/Testing/Cxx/TestStringToPath.cxx

@@ -46,7 +46,7 @@ protected:
 };
 
 //----------------------------------------------------------------------------
-int TestStringToPath(int argc, char *argv[])
+int TestStringToPath(int vtkNotUsed(argc), char *vtkNotUsed(argv)[])
 {
   // Set up a 2D context view, context test object and add it to the scene
   vtkNew<vtkContextView> view;