[docs] Update the check availability zone documentation

[esunar]

There is a new approach, how check availability zone described in the specification "JV001" and it's implementation is in progress 1.

The "check availability zone" documentation in "ceph-osd.rst" should be updated.

---

---

Imported from Launchpad using lp2gh.

• date created: 2021-10-13T09:55:11Z

• owner: rgildein

• assignee: rgildein

• the launchpad url

[esunar]

(by rgildein) PR: https://github.com/canonical/juju-verify/pull/35