Update README.md

remove unneded fact

Author: Marat Bakeev

README.md

@@ -77,7 +77,6 @@ Role Variables
       defined with the following dict:
         - `pool`: Name or UUID of the storage pool from which the volume should be
           allocated.
-        - `zfs_pool`: Set this option to `True`, if your pool is based on zfs (`pool type="zfs"` in your libvirt host setup). Only works with `disk` type volumes. A fact set by role `stackhpc.libvirt-host` is required.
         - `name`: Name to associate with the volume being created; For `file` type volumes include extension if you would like volumes created with one.
         - `file_path`: Where the image of `file` type volumes should be placed; defaults to `libvirt_volume_default_images_path`
         - `device`: `disk` or `cdrom`