Check disabling XFS_SUPPORT_V4 for cutting attack surface

The XFS V4 format is deprecated:
https://elixir.bootlin.com/linux/v6.3.11/source/fs/xfs/Kconfig#L25

Quote:
The V4 filesystem format lacks certain features that are supported
by the V5 format, such as metadata checksumming, strengthened
metadata verification, and the ability to store timestamps past the
year 2038. Because of this, the V4 format is deprecated. All users
should upgrade by backing up their files, reformatting, and restoring
from the backup... To close off an attack surface, say N.