docs: fix redirect

[317brian]

This deletes a markdown file in favor of the redirect file entry. Having both led to the following warning:

[WARNING] @docusaurus/plugin-client-redirects: multiple redirects are created with the same "from" pathname: "/docs/latest/ingestion/flatten-json.html"
It is not possible to redirect the same pathname to multiple destinations:
- {"from":"/docs/latest/ingestion/flatten-json.html","to":"/docs/latest/ingestion/flatten-json"}
- {"from":"/docs/latest/ingestion/flatten-json.html","to":"/docs/latest/ingestion/ingestion-spec"}

Having it doesn't break anything since it just gets ignored, but it's nice to get rid of a warning

Verify by running npm run build/yarn build, launching the site locally (like with http-server) and verifying that HOST:PORT/docs/latest/ingestion/flatten-json.html redirects to ingestion-spec

This PR has:

• been self-reviewed.

[amaechler]

Are we able to keep this redirect, and remove the flatten-json md file instead? That way, all the redirects would be kept in one place.

[317brian]

It's a tradeoff. We keep it all in one place, but redirects done this way always go to /latest since we didn't adopt Docusaurus's versioning feature. The one in the file will stay within the same version.

I don't have strong feelings about one over the other. Traditionally, I think we've just typically been fine with redirects always going to the latest version. So we can stick with tradition 🤣

[amaechler]

Should we split this into two entries? Since the Markdown file redirected to /docs/latest/ingestion/data-formats, we might want to keep that. But keep redirecting transform-spec to ingestion-spec.

Also, let's double-check the flatten-json redirection works as expected (maybe something is off, which would be why the markdown was added a couple of weeks ago?).

[vtlim]

Works for me 🦖