readdocs: MAAS datasource section is empty and link is broken

Bug Description

When looking for information about the MAAS datasource, I landed on [1]. That page is marked as TODO and the link should be updated to [3] or [4].

The closest to finding what the MAAS datasource does is the source code at [2].

1. https://cloudinit.readthedocs.io/en/latest/topics/datasources/maas.html
2. https://github.com/canonical/cloud-init/blob/4261ae538563d262bc76b8c55f7cc0c8abb14b00/cloudinit/sources/DataSourceMAAS.py
3. https://maas.io/
4. https://maas.io/docs

Thanks Alvaro.

https://github.com/canonical/cloud-init/pull/442

A fix for this was merged into cloud-init's master branch here: https://github.com/canonical/cloud-init/commit/615fe62c0927e68349a1cd602c169eb699684f50

Hi Alvaro, we've landed a fix for the broken link, and we already have bug 1858871 to capture writing the full documentation, so I recommend subscribing to that one for updates. Thanks again for making cloud-init better!

As this is a doc bug and the fix is available on ReadTheDocs, I'm going to mark this Fix Released.

Tracked in Github Issues as https://github.com/canonical/cloud-init/issues/3709