iwyu

This changes uses its best effort to clean up headers according to iwyu.

Reference:
https://include-what-you-use.org/

Signed-off-by: Nan Zhou <nanzhoumails@gmail.com>
Change-Id: Ibd8bd8735238d6ec101a2428241bb1727e3ac9a9
diff --git a/argument.cpp b/argument.cpp
index 389fa54..f0ee94d 100644
--- a/argument.cpp
+++ b/argument.cpp
@@ -15,9 +15,9 @@
  */
 #include "argument.hpp"
 
-#include <algorithm>
+#include <cstdlib>
 #include <iostream>
-#include <iterator>
+#include <utility>
 
 namespace phosphor::certs::util
 {