Removal of allowlist autopopulation migration tooling for CI job token

Summary

To support the migration of the default scope behavior for the CI job token allowlist, GitLab will be enabling automatic population of the allowlist as part of this effort. When the automation has occurred and the allowlist is enforced in %18.0, we will be removing the code that provides this automation.

Migration tooling was introduced in 17.7; planned removal is 18.4.