Fix typo in stroke-linejoin

[bmuenzenmeyer]

Fixes a typo in https://developer.mozilla.org/en-US/docs/Web/SVG/Attribute/stroke-linejoin#miter-clip and https://developer.mozilla.org/en-US/docs/Web/SVG/Attribute/stroke-linejoin#arcs

below vs bellow

I checked to make sure this wasn't an English vs American spelling - and am pretty certain it's just a mistake.

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[hamishwillee]

Thanks very much @bmuenzenmeyer !