Fixed broken links

[metalichen]

If this pull request addresses an open issue on the repository, please add 'Closes #NN' below, where NN is the issue number.

Please briefly summarise the changes made in the pull request, and the reason(s) for making these changes.
I discovered and fixed two broken links:

1. The link to the data page in the episode three didn't work because of the slash at the end
2. The link to the Genomics Workshop setup page in the setup was leading to setup.html, which doesn't seem to exist anymore

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[github-actions]

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[JCSzamosi]

This looks great, @metalichen! Thanks for the contribution. I'll merge it now.