Add xapian packages as buildrequirements for sphinx
Add xapian packages as buildrequirements for sphinx

In order to bump python-sphinx to match u-c [1] we need
xapian bindings in buildroot for rocky.

[1] https://review.rdoproject.org/r/#/c/12923

Change-Id: I5cc990c6b41a4dbe02fa426ae8f521722ef682b6

javierpena/rdoinfo,redhat-openstack/rdoinfo