include System.h to avoid warnings on windows in correct order

re #23268

Framework/Parallel/inc/MantidParallel/IO/NXEventDataLoader.h

@@ -4,6 +4,7 @@
 #include <H5Cpp.h>
 #include <vector>
 
+#include "MantidKernel/System.h"
 #include "MantidKernel/make_unique.h"
 #include "MantidParallel/DllConfig.h"
 #include "MantidParallel/IO/NXEventDataSource.h"

Framework/Parallel/src/IO/NXEventDataLoader.cpp

 #include "MantidParallel/IO/NXEventDataLoader.h"
-#include "MantidKernel/System.h"
 
 namespace Mantid {
 namespace Parallel {