Address reviewer feedback for #embed test

Remove defined(__has_embed) check and use since-cxx23 verify prefix to align with C++ DR test conventions.

Author: swote-git

clang/test/Preprocessor/cxx_oper_comma.cpp

@@ -3,8 +3,8 @@
 // RUN: %clang_cc1 -E -pedantic-errors %s -verify -std=c++14
 // RUN: %clang_cc1 -E -pedantic-errors %s -verify -std=c++17
 // RUN: %clang_cc1 -E -pedantic-errors %s -verify -std=c++20
-// RUN: %clang_cc1 -E -pedantic-errors %s -verify=expected,embed -std=c++23 -Wno-c23-extensions
-// RUN: %clang_cc1 -E -pedantic-errors %s -verify=expected,embed -std=c++2c -Wno-c23-extensions
+// RUN: %clang_cc1 -E -pedantic-errors %s -verify=expected,since-cxx23 -std=c++23 -Wno-c23-extensions
+// RUN: %clang_cc1 -E -pedantic-errors %s -verify=expected,since-cxx23 -std=c++2c -Wno-c23-extensions
 
 // Test 1: Top-level comma
 // expected-error@+1 {{expected end of line in preprocessor expression}}
@@ -39,7 +39,7 @@
 #endif
 
 // Test 7: Comma in #embed limit parameter (C++23+)
-#if defined(__has_embed) && __cplusplus >= 202302L
-// embed-error@+1 {{expected ')'}}
+#if __cplusplus >= 202302L
+// since-cxx23-error@+1 {{expected ')'}}
 #embed "jk.txt" limit(1, 2)
 #endif