typo error in 'Ceph RBD' segment of readme
typo error in 'Ceph RBD' segment of readme

Signed-off-by: yutao <507fd338a96f66b561d11fce4583332ac7472dfd@chinacloud.com.cn>

kubernetes/examples,kubernetes/examples,kubernetes/examples,kubernetes/examples,kubernetes/examples,kubernetes/examples,kubernetes/examples,kubernetes/examples