[libcxx] Add missing c++98 xfail. NFC.

This is the only test failing in c++98 mode at the moment.

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@281731 91177308-0d34-0410-b5e6-96231b3b80d8

test/std/iterators/iterator.range/begin-end.pass.cpp

@@ -7,7 +7,7 @@
 //
 //===----------------------------------------------------------------------===//
 
-// XFAIL: c++03
+// XFAIL: c++03, c++98
 
 // <iterator>
 // template <class C> auto begin(C& c) -> decltype(c.begin());