Disable registration tokens for all instances except GitLab.com
See more at Replace FF with settings migration in runner to... (!122316 - merged) and https://docs.gitlab.com/ee/architecture/blueprints/runner_tokens
To encourage users to migrate to the new architecture, we update ApplicationSetting.allow_runner_registration_token = false
for every instance except gitlab.com.
Users can still flip this setting back to true
until %18.0.