ceph: fix a wrong link
ceph: fix a wrong link

There is a wrong link to the monitoring document.

Signed-off-by: Satoru Takeuchi <0be322b419f8cd46ee75447832ef0476dff222bc@gmail.com>

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