Remove an extra include from NullPtr.h

Review URL: https://codereview.chromium.org/334373004

git-svn-id: svn://svn.chromium.org/blink/trunk@176287 bbb929c8-8fbe-4397-9dbb-9b2b20218538

third_party/WebKit/Source/wtf/NullPtr.h

@@ -31,8 +31,6 @@ SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 // nullptr_t type and nullptr object. They are defined in the same namespaces they
 // would be in compiler and library that had the support.
 
-#include <ciso646>
-
 #if COMPILER_SUPPORTS(CXX_NULLPTR) || defined(_LIBCPP_VERSION)
 
 #include <cstddef>