Update docs/clustering.md
Update docs/clustering.md

Co-Authored-By: Dieterbe <b617834f89be0c2a85d223f602f0a5edf9446141@plaetinck.be>
raintank/raintank-metric,raintank/metrictank,replay/metrictank,raintank/metrictank,raintank/metrictank,replay/metrictank,raintank/raintank-metric,replay/metrictank,raintank/raintank-metric,raintank/metrictank,replay/metrictank