SWDEV-284682 - Revert Workaround RTC macro in vector types

Re-enable __HIPCC_RTC__ in hip_vector_types.h which require
an upstream clang patch, 6823af0ca858b54e09e5be61a19d067ccd0bd6b7.
Once upstream patch has landed in mainline, merge this for
hiprtc functionality.

Change-Id: Ife884e0c3081b307bdadc8bec7804d1d7c60153b

hipamd/include/hip/amd_detail/amd_hip_vector_types.h

@@ -44,12 +44,11 @@ THE SOFTWARE.
     #endif
 
 #if defined(__cplusplus)
-// FIXME: Temporarily enable C++ headers while mainline headers is outdated.
-//#if !defined(__HIPCC_RTC__)
+#if !defined(__HIPCC_RTC__)
     #include <array>
     #include <iosfwd>
     #include <type_traits>
-//#endif // !defined(__HIPCC_RTC__)
+#endif // !defined(__HIPCC_RTC__)
 
     namespace hip_impl {
         template<typename, typename, unsigned int> struct Scalar_accessor;