[SYCL] Remove workaround after fix in spec

KhronosGroup/SYCL-Docs#40 fix was submitted.

sycl/include/CL/sycl/aliases.hpp

@@ -24,12 +24,6 @@ class half;
 } // namespace sycl
 } // __SYCL_INLINE_NAMESPACE(cl)
 
-// FIXME: line below exports 'half' into global namespace, which seems incorrect
-// However, SYCL 1.2.1 spec considers 'half' to be a fundamental C++ data type
-// which doesn't exist within the 'cl::sycl' namespace.
-// Related spec issue: KhronosGroup/SYCL-Docs#40
-using half = cl::sycl::detail::half_impl::half;
-
 #define __SYCL_MAKE_VECTOR_ALIAS(ALIAS, TYPE, N)                               \
   using ALIAS##N = cl::sycl::vec<TYPE, N>;