generic/673: fix golden output to reflect vfs setgid behavior

generic/673: fix golden output to reflect vfs setgid behavior

Filipe Manana pointed out[1] that the setgid dropping behavior encoded
in this generic test is based on some outdated XFS code, and not based
on what the VFS inode attribute change functions actually do.  Now that
we're working on fixing that, we should update the golden output to
reflect what all filesystems are supposed to be doing.

[1] https://lore.kernel.org/linux-xfs/CAL3q7H47iNQ=Wmk83WcGB-KBJVOEtR9+qGczzCeXJ9Y2KCV25Q@mail.gmail.com/

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Zorro Lang <zlang@redhat.com>
Signed-off-by: Eryu Guan <guaneryu@gmail.com>