[UT] Include iomanip if not defined (#1510)

* [UT] Include iomanip if not defined

Signed-off-by: nileshnegi <Nilesh.Negi@amd.com>

* Remove include guards

`iomanip.h` has pre-defined include guards. These are not needed.

Co-authored-by: corey-derochie-amd <161367113+corey-derochie-amd@users.noreply.github.com>

---------

Signed-off-by: nileshnegi <Nilesh.Negi@amd.com>
Co-authored-by: corey-derochie-amd <161367113+corey-derochie-amd@users.noreply.github.com>

[ROCm/rccl commit: 4e406acc43]

projects/rccl/test/common/TestBed.hpp

@@ -10,6 +10,7 @@
 #include "TestBedChild.hpp"
 #include "EnvVars.hpp"
 #include <gtest/gtest.h>
+#include <iomanip>
 
 namespace RcclUnitTesting
 {