container: plugins: root: fix example3()'s usage of throw handler

The old macros should *not* have been used in any example; as they
were intended for internal use only.

This was noted in Doxygen ...by not noting them as publicly consumable.

container/plugins/root/example.cc

@@ -108,7 +108,7 @@ void example2()
 //! \ingroup cpp_plugin_impl
 void example3()
 {
-  namespace common = ::dfi::macro::common;
+  namespace common = ::dfi::common;
 
   const std::string base{
       common::get_env("global_basename") + " "
@@ -122,10 +122,8 @@ void example3()
 
   auto exec_cmd = [&make_cmd](const std::string& cmd) {
     // shell 0 = success
-    THROW_IF(
-        common::exec("bash -i -c '" + make_cmd(cmd) + "'"),
-        std::runtime_error,
-        "command failed")
+    common::throw_ex_if<common::type::RuntimeError>(
+        common::exec("bash -i -c '" + make_cmd(cmd) + "'"), "command failed");
   };
 
   std::cout << "\nImporting journals...\n";