[libcxx] [test] improve expected/nodiscrard.verify

Author: hulxv

libcxx/test/libcxx/utilities/expected/expected.expected/nodiscard.verify.cpp

@@ -6,11 +6,11 @@
 //
 //===----------------------------------------------------------------------===//
 
-// UNSUPPORTED: c++03, c++11, c++14, c++17
+// REQUIRES: std-at-least-c++23
 
 // <expected>
 
-// Test that std::expected generates [[nodiscard]] warnings
+// Test that ignoring std::expected generates [[nodiscard]] warnings.
 
 #include <expected>
 
@@ -28,4 +28,4 @@ void test() {
 
   // expected-warning@+1 {{ignoring return value of function declared with 'nodiscard' attribute}}
   returns_expected_void();
-}
+}