fix(docs): adjust explanation of columns' name 🖍

[mesqueeb]

I had a really hard time understanding the difference between row-key which is often set to name in the examples here, and the name field on the columns object.

I know in retrospect it's a really simple difference: columns each have a name and rows each have an id or something to be set with row-key.

But I believe that the row-key has nothing to do with the columns name field if I'm not mistaken. So writing "used by row-key" at the columns name only further confused me. 😅

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