[CI:DOCS] Fix readthedocs link
Touch up the link to the docs on readthedocs.  Using the fully
specified link like this will cause a CORS issue in many browsers.
Plus we're working on a Spanish variant of the site, so we probably
should point to the English variant.
# Podman Documentation
The online man pages and other documents regarding Podman can be found at
-[Read The Docs](https://podman.readthedocs.io/en/latest/index.html). The man pages
+[Read The Docs](https://podman.readthedocs.io). The man pages
can be found under the [Commands](https://podman.readthedocs.io/en/latest/Commands.html)
link on that page.
