docs: Improve wiki on how to verify new board variants #2559
Description
https://github.com/stm32duino/Arduino_Core_STM32/wiki/Add-a-new-variant-%28board%29#6---restart does not explain how to verify the new changes.
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https://github.com/stm32duino/Arduino_Core_STM32/wiki/Add-a-new-variant-%28board%29#6---restart does not explain how to verify the new changes.