Update the Standard Library Header Units test for attributes (#1747)

tests/std/tests/P1502R1_standard_library_header_units/env.lst

@@ -7,7 +7,7 @@ PM_CL="/w14365 /D_ENFORCE_FACET_SPECIALIZATIONS=1"
 RUNALL_CROSSLIST
 PM_CL="/w14640 /Zc:threadSafeInit- /EHsc /std:c++latest"
 RUNALL_CROSSLIST
-PM_CL="/Zc:preprocessor /D_SILENCE_CXX17_STRSTREAM_DEPRECATION_WARNING"
+PM_CL="/Zc:preprocessor /D_SILENCE_CXX17_STRSTREAM_DEPRECATION_WARNING /D_SILENCE_CXX17_CODECVT_HEADER_DEPRECATION_WARNING"
 RUNALL_CROSSLIST
 PM_CL="/MD"
 PM_CL="/MDd"

tests/std/tests/P1502R1_standard_library_header_units/test.cpp

@@ -206,7 +206,7 @@ int main() {
         assert(conv.from_bytes(utf8_koshka_cat) == utf16_koshka_cat);
         assert(conv.to_bytes(utf16_koshka_cat) == utf8_koshka_cat);
 
-        static_assert(static_cast<int>(codecvt_mode::consume_header) == 4); // TRANSITION, DevCom-1160041 (deprecated)
+        static_assert(static_cast<int>(codecvt_mode::consume_header) == 4);
     }
 
     {