Update any links that point to obsolete documentation sites

[eecavanna]

Background

We are in the process of instituting redirects from our obsolete documentation sites to the new, centralized one at https://docs.microbiomedata.org. If the links in our documentation source files used relative URLs, we are good to go. However, if the links used absolute URLs, when people visit those links, their web browser will do an unnecessary "hop" (i.e. first visiting the obsolete site, then getting redirected to the new site).

Task

The task here is to update any links that point to obsolete documentation sites, so that they point to the new site directly.

Urgency

Low — the links will still work even with the extra "hop" involved.

[eecavanna]

Here are some: