In https://gitlab.com/gitlab-org/gitlab/-/merge_requests/77829, we
waived the credit card validation requirement for namespaces with paid
CI/CD minutes.

In https://gitlab.com/gitlab-org/gitlab/-/merge_requests/78591, we
enabled this feature by default.

This commit drops this feature flag altogether.

Relates to https://gitlab.com/gitlab-org/gitlab/-/issues/349841

Changelog: changed