update .clang-format

Added the header inclusion order to the .clang-format file generated
these changes.

Change-Id: I4f51a20f469de431ee6a5ba78e3f4da39c980fab
Signed-off-by: Patrick Venture <venture@google.com>
diff --git a/src/test/callbackgroupgentest.cpp b/src/test/callbackgroupgentest.cpp
index fe760ec..64811d7 100644
--- a/src/test/callbackgroupgentest.cpp
+++ b/src/test/callbackgroupgentest.cpp
@@ -1,7 +1,9 @@
+#include "data_types.hpp"
+
 #include <array>
 #include <string>
+
 #include <gtest/gtest.h>
-#include "data_types.hpp"
 
 using namespace phosphor::dbus::monitoring;