chore: drop `SEC_REGISTRY_IMAGE`
What does this MR do?
Drops hardcoded var in favor CI variable, see discussion secrets!139 (comment 839216195)
What are the relevant issue numbers?
Relates to https://gitlab.com/gitlab-org/gitlab/-/issues/334325
Does this MR meet the acceptance criteria?
- [-] Changelog entry added
-
Documentation created/updated for GitLab EE, if necessary -
Documentation created/updated for this project, if necessary -
Documentation reviewed by technical writer or follow-up review issue created -
Tests added for this feature/bug -
Job definition updated, if necessary -
Conforms to the code review guidelines - [-] Conforms to the Go guidelines
- [-] Security reports checked/validated by reviewer