docs: fix a typo in a Markdown link

[nhoizey]

Description

Documentation

Related Issues

[gillkyle]

Thanks for the fix @nhoizey!

[gatsbot]

Holy buckets, @nhoizey — we just merged your PR to Gatsby! 💪💜

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Thanks again!

[nhoizey]

Thanks for the fix @nhoizey!

you're welcome!