Stop trying to publish the unstable spec

[richvdh]

This hasn't really worked properly since matrix-doc was redesigned to use hugo, but we still had a few vestiges of the old code hanging around. In particular, there is no need to fetch the matrix-doc assets, and no need to attempt to style them.

I've also removed update_docs_local.sh since its purpose was unclear.

Preview: https://pr1092--matrix-org-previews.netlify.app

[afranke]

If build-spec is effectively going to do the same thing to the same committed files over and over again, considering any future version of the spec goes through a different process now, is there a point in keeping this at all? Couldn’t we just commit the styled files once and for all?

[afranke]

And just to confirm:

• I am in favour of going in the direction of this PR, I just think it doesn’t go far enough.
• the parts removed by @richvdh are already effectively useless, as the assets.tar.gz artifact only contains unstable.json nowadays, which we then copy over but don’t actually use anywhere (and https://matrix.org/docs/spec/client_server/unstable.json redirects to the new spec site)

[richvdh]

If build-spec is effectively going to do the same thing to the same committed files over and over again, considering any future version of the spec goes through a different process now, is there a point in keeping this at all? Couldn’t we just commit the styled files once and for all?

I'm reluctant to do this, as it ties the spec to the same rendering forever more, even if the matrix.org homeserver gets a rebrand. And yes, in future, maybe we'll find alternative hosting for old versions of the spec, but we aren't there yet, so for now let's keep it as-is.

[richvdh]

In view of the lack of objections, I'm going to take the executive decision to merge this.