[gn build] Port 4dfa75c

Author: llvmgnsyncbot

llvm/utils/gn/secondary/libcxx/include/BUILD.gn

@@ -863,7 +863,6 @@ if (current_toolchain == default_toolchain) {
       "__type_traits/is_referenceable.h",
       "__type_traits/is_same.h",
       "__type_traits/is_scalar.h",
-      "__type_traits/is_scoped_enum.h",
       "__type_traits/is_signed.h",
       "__type_traits/is_signed_integer.h",
       "__type_traits/is_specialization.h",