Fix code format for Accelerate doc
This PR fixes the format of externally linked code objects so they don't render like this:

![Screen Shot 2022-01-25 at 1 30 26 PM](https://user-images.githubusercontent.com/59462357/151076016-482c4d6e-473a-44f8-a504-b7ab3e0dacd4.png)

Also replaces the side-by-side image with a code block because the image isn't easily visible to users.
_The documentation is not available anymore as the PR was closed or merged._