annotations_of: アノテーションの文字列リテラルはdefine_static_stringでラップする必要がある

Co-authored-by: Raclamusi <61970673+Raclamusi@users.noreply.github.com>

Author: faithandbrave

reference/meta/annotations_of.md

@@ -26,7 +26,7 @@ namespace std::meta {
 
 struct Label { const char* text; };
 
-struct [[=Label{"my struct"}, =42]] S {};
+struct [[=Label{std::define_static_string("my struct")}, =42]] S {};
 
 int main() {
   constexpr auto annots = std::meta::annotations_of(^^S);