Rename, archive, and drop hosting

[dcroote]

https://api3workspace.slack.com/archives/C01N6001YCE/p1721838165339709

Since these docs are now support only old legacy versions of services (e.g. Airnode version <= 10) I think it is safe to rename the repo to old-api3-docs, archive the repo, and drop firebase hosting (https://old-docs.api3.org/). If someone, for some reason, truly needs these docs, this repo could always be cloned and built locally for viewing and searching. Existing links to https://old-docs.api3.org/ could be redirected here to this repo's README. CC @wkande @Siegrift @Ashar2shahid