doc: update doc to add stable-3.2 information
doc: update doc to add stable-3.2 information

Since the branch has been created, we must reflect it in the doc.

Signed-off-by: Guillaume Abrioux <30a9df5a0293a6108675377fa1673f7aa713f915@redhat.com>

ceph/ceph-ansible,ceph/ceph-ansible,fgal/ceph-ansible,fgal/ceph-ansible