update list and order of include files from include-what-you-use analysis

src/atom_vec_body.cpp

@@ -112,7 +112,7 @@ void AtomVecBody::process_args(int narg, char **arg)
 #define BodyStyle(key,Class) \
   } else if (strcmp(arg[0],#key) == 0) { \
     bptr = new Class(lmp,narg,arg);
-#include "style_body.h"
+#include "style_body.h"  // IWYU pragma: keep
 #undef BodyStyle
 #undef BODY_CLASS