[modbus] Clarify poller names must be unique (#5759)
[modbus] Clarify poller names must be unique (#5759)

* Update README.md

Clarify poller names must be unique

* Update README.md

reworded 'unique' thing ID requirement

Signed-off-by: Ross Kennedy <a3825ada0bb187f179640e5a291e80e2d6930274@culzean.clara.co.uk>

* Update bundles/org.openhab.binding.modbus/README.md

I guess I should sign that off like the previous edits

Signed-off-by: Ross Kennedy <a3825ada0bb187f179640e5a291e80e2d6930274@culzean.clara.co.uk>

Co-Authored-By: Christoph Weitkamp <64b2b6d12bfe4baae7dad3d018f8cbf6b0e7a044@christophweitkamp.de>

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