fix image rendering in rapid-sagemaker-hpo notebook

[ncclementi]

Closes #468

Let's give it a try and see what happens in the rendering when using markdown-style hyperlinks.

Edit: I check the read the doc link and looks like it works 🚀

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[jameslamb]

Thanks for this! Looks good to me in the docs too.

And I checked the repo for other stuff like this, didn't find any more.

git grep -E 'img.*src'

Appreciate the help!