[Samba] Suggested documentation update: remove reference to CONFIG_EXT4_FS_XATTR

[outlook_FEDB99F04FA54CA1@outlook.com]

It seems this configuration option no longer appears in recent kernels, and that's been true for a while now; but it's referenced at:

https://wiki.samba.org/index.php/Operating_system_requirements/File_system_support

It might be helpful to remove the reference to that (or at least indicate that it's only needed on older kernels) in the wiki page. Thanks.