Remove hack to get relative markdown links in JSDocs to work with typedoc

[pokey]

In #1225, we introduced a hack to rewrite markdown links that appear in JSDocs to work around typedoc2md/typedoc-plugin-markdown#394, which was the cause of CI failures such as https://github.com/cursorless-dev/cursorless/actions/runs/4022134484/jobs/6911611154. We'd like to remove this hack once that issue is resolved

• Also set onBrokenMarkdownLinks back to throw, keeping an eye on `onBrokenMarkdownLinks` vs `onBrokenLinks` facebook/docusaurus#8613 to see if we can switch it to throw even before typedoc issue is fixed, or if having it at throw is even desirable

[pokey]

Realised VSCode hover wasn't actually working. Without that constraint, it's not hard to get these links to work, as we don't need to do any re-writing; we just have them be what docusaurus wants in the first place.

See typedoc2md/typedoc-plugin-markdown#394 (comment)