docs: fix indentation
docs: fix indentation

Fix indentation for `monitoring:` block example.  It belongs inside the
`spec:`.

Signed-off-by: Robert Spier <c9484850f6ee3d3fb73f3c3345f26ec064da35e4@pobox.com>

rook/rook,rook/rook,rook/rook,rook/rook,rook/rook