Disable release key in gitlab-ci.yaml

The following discussions from !19298 (merged) should be addressed:

• @sean_carroll started a discussion: (+3 comments)

  Thanks @ayufan

  I think that this is a first step, as it misses the persisting of the release: anywhere. We only parse it.

  I'm not clear on that, I would have expected it to be already persisted in ci_builds.options with the rest of the .gitlab-ci.yaml.

  I have opened a new issue to handle the persistence. Could you possibly point me to where persistence is handled for the rest of the yaml?

• @ayufan started a discussion:

  Since it is not yet supported, can we add?

              validates :config,
                disallowed_keys: {
                  in: %i[release],
                  message: 'release features are not enabled'
                },
                unless: -> { Feature.enabled?(:ci_release_generation, default_enabled: false) }