ceph: update cleanupPolicy design doc
ceph: update cleanupPolicy design doc

Cleanup Policy design doc is not up to date to with respect to latest implementation. This PR updates the design doc.

Signed-off-by: Santosh Pillai <a9a1d71426d37777113fca9df086b5a94f580e95@redhat.com>

rook/rook,rook/rook,rook/rook,rook/nfs,rook/nfs,rook/rook,rook/rook,rook/nfs