Fix broken link to Lumo Colors

[rodolforfq]

The "Lumo Colors" link at https://vaadin.com/docs/latest/styling/lumo/lumo-variants redirects to https://vaadin.com/styling/lumo/lumo-style-properties/color which results in a 404 error. The corrected link now takes you to the correct page: https://vaadin.com/docs/latest/styling/lumo/lumo-style-properties/color

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[jouni]

Thanks for noticing 👍