Make `os.DirEntry.is_symlink` ~twice as fast

[sobolevn]

While fixing a merge conflict in #108718 I've noticed that I've missed the same problem in os.DirEntry.is_symlink.

I will send a new PR since the original one was already merged

Refs #108717

Linked PRs

• gh-108985: Make os.DirEntry.is_symlink ~twice as fast #108986

[sobolevn]

False alarm:

#elif defined(HAVE_DIRENT_D_TYPE)
    /* POSIX */
    if (self->d_type != DT_UNKNOWN)
        return self->d_type == DT_LNK;
    else
        return DirEntry_test_mode(defining_class, self, 0, S_IFLNK);
#else
    /* POSIX without d_type */
    return DirEntry_test_mode(defining_class, self, 0, S_IFLNK);
#endif