fix typo in ceph-managed-disruptionbudgets.md
fix typo in ceph-managed-disruptionbudgets.md

Signed-off-by: Sakura <f49b857957a4860b7ac562d17b4e800ab67560f4@daocloud.io>

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