Fix up node_md_disks changelog entry
Fix up node_md_disks changelog entry

Fixes: https://github.com/prometheus/node_exporter/issues/1759

Signed-off-by: Ben Kochie <9bbf917dc63fbaa40c67921332d26cf16a50db75@gmail.com>

siavashs/node_exporter,prometheus/node_exporter,siavashs/node_exporter,siavashs/node_exporter,siavashs/node_exporter,prometheus/node_exporter,prometheus/node_exporter