Updates docs to fix incorrect container example

Existing container was out of date and did not work
for the db restore example. Updates to a rocky-9
example.

Change-Id: I5f57467a18d3e42e0c71826cc3a7740110162af7
(cherry picked from commit 3564f9de)

doc/source/admin/mariadb-backup-and-restore.rst

@@ -83,7 +83,7 @@ following options on the first database node:
 
    docker run --rm -it --volumes-from mariadb --name dbrestore \
       --volume mariadb_backup:/backup \
-      quay.io/openstack.kolla/centos-source-mariadb-server:|KOLLA_OPENSTACK_RELEASE| \
+      quay.io/openstack.kolla/mariadb-server:|KOLLA_OPENSTACK_RELEASE|-rocky-9 \
       /bin/bash
    (dbrestore) $ cd /backup
    (dbrestore) $ rm -rf /backup/restore
@@ -105,7 +105,7 @@ place, again on the first node:
 
    docker run --rm -it --volumes-from mariadb --name dbrestore \
       --volume mariadb_backup:/backup \
-      quay.io/openstack.kolla/centos-source-mariadb-server:|KOLLA_OPENSTACK_RELEASE| \
+      quay.io/openstack.kolla/mariadb-server:|KOLLA_OPENSTACK_RELEASE|-rocky-9 \
       /bin/bash
    (dbrestore) $ rm -rf /var/lib/mysql/*
    (dbrestore) $ rm -rf /var/lib/mysql/\.[^\.]*
@@ -148,7 +148,7 @@ incremental backup,
 
    docker run --rm -it --volumes-from mariadb --name dbrestore \
       --volume mariadb_backup:/backup --tmpfs /backup/restore \
-      quay.io/openstack.kolla/centos-source-mariadb-server:|KOLLA_OPENSTACK_RELEASE| \
+      quay.io/openstack.kolla/mariadb-server:|KOLLA_OPENSTACK_RELEASE|-rocky-9 \
       /bin/bash
    (dbrestore) $ cd /backup
    (dbrestore) $ rm -rf /backup/restore