stable version of docs not building

[ethanwhite]

This results in the current version being marked as unstable:

1. The failing build is due to Stable instead of stable (but I can't figure out where Stable is coming from.
2. By default the latest semantic version tag should become stable on readthedocs without the use of a stable tag (but deleting our stable tag didn't see to fix things)
3. Apparently we aren't using version_switcher.json anymore? Because 1.5.0 isn't present there, but it's still showing up in the menu on readthedocs.
4. All other projects I've checked have stable not Stable, including projects that have no tag for stable, they just let readthedocs do its thing

Bug report submitted to readthedocs: readthedocs/readthedocs.org#11939

[bw4sz]

Can this be closed?

[henrykironde]

We're currently using the version_switcher.json but need to update it. It still feels a bit redundant, though, it's structured the same way PyData handles it.

We also have the default Read the Docs version switcher at the bottom of the page.