remove `react-markdown` from the Tooltip component

[iAdramelk]

Right now Tooltip uses react-markdown to render descriptions from content/docs/glossary.js to HTML. It was ok then we have to use react-markdown to render docs pages, but now we should simplify it.

We can either convert md to html on the server side with gatsby, or just replace it with plain html, because right now we only have couple of links and code samples there.

• Address glossary: auto link dvc <cmd> strings like in docs #1137 after this one.

[shcheklein]

We should probably do We can either convert md to html on the server side with gatsby . But it feels it won't save us much. Would be great first to do a comparison on how much JS and load time we can shave off with this effort.

[rogermparent]

I can do this one in a way similar to the way I did Event expiration: loading the data from glossary.js into GraphQL nodes and processing it at build time will allow us to freely parse the MD into HTML during build time with any method- probably Remark, since we use it in other features similar to this like descriptionLong.

With build-time HTML, we can get rid of react-markdown completely as this tooltip feature is the only dependent of it in the codebase from what I can tell.