Update GitHub actions to only update docs based on release

[JoblersTune]

Currently changes are made instantly to rafiki.dev docs whenever documentation content is merged into main. This means the live docs are slightly ahead of the current released Rafiki version. It would be better to only update the docs when a new version is tagged so that they keep in sync.

[mkurapov]

@tadejgolobic something to note once we begin using the new release process

[mkurapov]

See: https://starlight-versions.vercel.app/