docs: update URLs to point to the RTD links

Fixes #5798
Signed-off-by: Kefu Chai <tchaikov@gmail.com>

README.rst

@@ -2,7 +2,7 @@ ceph-ansible
 ============
 Ansible playbooks for Ceph, the distributed filesystem.
 
-Please refer to our hosted documentation here: http://docs.ceph.com/ceph-ansible/master/
+Please refer to our hosted documentation here: https://docs.ceph.com/projects/ceph-ansible/en/latest/
 
 You can view documentation for our ``stable-*`` branches by substituting ``master`` in the link
-above for the name of the branch. For example: http://docs.ceph.com/ceph-ansible/stable-3.0/ 
+above for the name of the branch. For example: https://docs.ceph.com/projects/ceph-ansible/en/stable-5.0/