Mark tests as unsupported in C++98 as well

[rogfer01]

ChangeLog:

• I wanted to mark two tests but forgot to add one in the previous change

[mclow.lists]

LGTM

[rogfer01]

Thank you @mclow.lists !

test/std/re/re.alg/re.alg.match/exponential.pass.cpp

 //===----------------------------------------------------------------------===//
 //
 //                     The LLVM Compiler Infrastructure
 //
 // This file is dual licensed under the MIT and the University of Illinois Open
 // Source Licenses. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
 
 // <regex>
 // UNSUPPORTED: libcpp-no-exceptions
-// UNSUPPORTED: c++03
+// UNSUPPORTED: c++98, c++03
 
 // template <class BidirectionalIterator, class Allocator, class charT, class traits>
 //     bool
 //     regex_match(BidirectionalIterator first, BidirectionalIterator last,
 //                  match_results<BidirectionalIterator, Allocator>& m,
 //                  const basic_regex<charT, traits>& e,
 //                  regex_constants::match_flag_type flags = regex_constants::match_default);