Correct LanguageExtensions.rst

The feature was in fact backported to C++98

Author: zyn0217

clang/docs/LanguageExtensions.rst

@@ -1641,7 +1641,7 @@ Conditional ``explicit``                      __cpp_conditional_explicit       C
 Attributes on Lambda-Expressions                                               C++23         C++11
 Attributes on Structured Bindings             __cpp_structured_bindings        C++26         C++03
 Packs in Structured Bindings                  __cpp_structured_bindings        C++26         C++03
-Structured binding declaration as a condition                                  C++26         C++11
+Structured binding declaration as a condition __cpp_structured_bindings        C++26         C++98
 Static assert with user-generated message     __cpp_static_assert >= 202306L   C++26         C++11
 Pack Indexing                                 __cpp_pack_indexing              C++26         C++03
 ``= delete ("should have a reason");``        __cpp_deleted_function           C++26         C++03