Removed using causing ambiguity error.

Author: vladimirlaz

sycl/test/regression/disabled_std_byte.cpp

@@ -1,7 +1,6 @@
 // RUN: %clangxx -fsycl -fsyntax-only -Xclang -verify -D_HAS_STD_BYTE=0 %s -Xclang -verify-ignore-unexpected=note,warning
 // RUN: %clangxx -fsycl -fsyntax-only -Xclang -verify %s -Xclang -verify-ignore-unexpected=note,warning
 // expected-no-diagnostics
-using namespace ::std;
 #include <CL/sycl.hpp>
 #include <algorithm>
 #ifdef _WIN32