Fix test header

Author: sergey-semenov

sycl/test-e2e/Regression/unwaited_for_host_task.cpp

@@ -1,7 +1,7 @@
 // RUN: %{build} -o %t.out
 // RUN: %{run} %t.out
 
-#include <sycl/sycl.hpp>
+#include <sycl/detail/core.hpp>
 
 using namespace sycl;