Remove ci_job_token_groups_allowlist feature flag

Rollout issue: #439611 (closed) Original issue: #435903 (closed) Original MR: !142441 (merged)

In the scope of the rollout issue Remove ci_job_token_groups_allowlist feature flag of Backend: API allowing projects to add groups in their CI_JOB_TOKEN allowlist, following the global activation on production environments and testing, it is necessary to deactivate this feature flag.

Changelog: other

MR acceptance checklist

Please evaluate this MR against the MR acceptance checklist. It helps you analyze changes to reduce risks in quality, performance, reliability, security, and maintainability.

Screenshots or screen recordings

Screenshots are required for UI changes, and strongly recommended for all other merge requests.

Before	After

How to set up and validate locally

Numbered steps to set up and validate the change are strongly suggested.