Bump the remained minimum Ansible version to 2.9

It should be bumped by [1], but missing, this PS to
be supplement.

[1]: https://review.opendev.org/#/c/753776/2

Depends-On: I5befc72a4894d625ca352b27df9d3aa84a2f5b2c
Change-Id: I75742653cb62c27317abf297a0143399d6adc644

doc/source/user/quickstart.rst

@@ -111,7 +111,7 @@ If installing Kolla Ansible in a virtual environment, skip this section.
       sudo pip install -U pip
 
 #. Install `Ansible <http://www.ansible.com>`__. Kolla Ansible requires at least
-   Ansible ``2.8`` and supports up to ``2.9``.
+   Ansible ``2.9`` and supports up to ``2.9``.
 
    For CentOS or RHEL, run: