Move to more modern headers

We had a couple places where the c style headers got checked in for

Tested:  Code builds.

Signed-off-by: Ed Tanous <ed.tanous@intel.com>
Change-Id: Iebfbd846033618ff972825a0a9f89e8d05395ce8
diff --git a/redfish-core/lib/sensors.hpp b/redfish-core/lib/sensors.hpp
index a03c13c..fb3b25e 100644
--- a/redfish-core/lib/sensors.hpp
+++ b/redfish-core/lib/sensors.hpp
@@ -17,12 +17,11 @@
 
 #include "node.hpp"
 
-#include <math.h>
-
 #include <boost/algorithm/string/predicate.hpp>
 #include <boost/algorithm/string/split.hpp>
 #include <boost/container/flat_map.hpp>
 #include <boost/range/algorithm/replace_copy_if.hpp>
+#include <cmath>
 #include <dbus_singleton.hpp>
 #include <utils/json_utils.hpp>
 #include <variant>