Fix broken links

[brian-rose]

The nightly build has been failing for months due to link problems. This PR should get it passing again.

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[brian-rose]

The link checker seems to be checking the unmodified sources instead of the modified sources in the PR. I have no idea why.

[brian-rose]

The link checker seems to be checking the unmodified sources instead of the modified sources in the PR. I have no idea why.

Nope, it was user error, I didn't catch all the offending links in my previous commits. Should be good to go now.

[brian-rose]

Note to whoever reviews this, the MATLAB links are not broken but they are refusing our link checker. If we kept the links, we would have to add explicit exceptions to the link checker, like we do in the Cookbook template.

Getting rid of links to MATLAB seemed like a simpler and better solution.