COMP: Fix test method signature in FEM module

Fix test method signature in `FEM` module: replacing `char ** argv` with
`char * argv[]`.

Increase consitency with the ITK SW Guidelines.

Follow-up to several commits, e.g. 490f00d, 7b5d438, 39b3c62, 18e272c,
and 9ffaab4.

Modules/Numerics/FEM/test/itkFEMFactoryTest.cxx

@@ -20,7 +20,7 @@
 #include "itkTestingMacros.h"
 
 int
-main(int argc, char ** argv)
+main(int argc, char * argv[])
 {
   if (argc != 2)
   {