Wait for new butane/ignition spec support to land in stable before updating the docs

[travier]

We should wait for bumps like #793 until support lands in stable.

See: https://hachyderm.io/@def/116193116733674306

[dustymabe]

We should wait for bumps like #793 until support lands in stable.

I agree, but hopefully whatever solution we come up with can be automated.

On GitHub I wish there was a "I approve of this PR, please merge it after 3 weeks" option 😄