vagrant: update centos image to 8.2
vagrant: update centos image to 8.2

CentOS 8.2 (2004) has been relesed so we should switch to this image
when using vagrant.

Signed-off-by: Dimitri Savineau <a50a620e679eed14f4e99998b821cea8884cf228@redhat.com>

ceph/ceph-ansible,ceph/ceph-ansible