Backport 'Remove Helm based release environment QA' to 18-11-stable-ee

What does this MR do and why?

Backport of the following to 18-11-stable-ee:

• e9eb0666 - Pass down DOCKER_VERSION to release env pipeline (https://gitlab.com/gitlab-com/gl-infra/production/-/work_items/22168)
• 6c18faff - Remove Helm based release environment QA (gitlab-com/gl-infra/delivery#21596 (closed))
• fc68b7bc - Do not allow release environment omnibus builds to fail (gitlab-com/gl-infra/delivery#21244 (closed))

The Helm based release environments don't work with GitLab chart for version 19.0 and above anymore. This removes the old Helm-based QA job and promotes the GET-based QA job as the primary one. DOCKER_VERSION was missing from the inherited variables passed to the child pipeline. The Omnibus build jobs are now stable and should not be allowed to fail silently.

References

• Original MR: !237032 (merged)
• gitlab-com/gl-infra/delivery#21596 (closed)
• https://gitlab.com/gitlab-com/gl-infra/production/-/work_items/22168
• gitlab-com/gl-infra/delivery#21244 (closed)

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• This MR is backporting a bug fix, documentation update, or spec fix, previously merged in the default branch.
• The MR that fixed the bug on the default branch has been deployed to GitLab.com (not applicable for documentation or spec changes).
• The MR title is descriptive (e.g. "Backport of 'title of default branch MR'"). This is important, since the title will be copied to the patch blog post.
• Required labels have been applied to this merge request
  • severity label and bug subtype labels (if applicable)
  • If this MR fixes a bug that affects customers, the customer label has been applied.
• This MR has been approved by a maintainer (only one approval is required).
• Ensure the e2e:test-on-omnibus-ee job has succeeded, or if it has failed, investigate the failures. If you determine the failures are unrelated, you may proceed. If you need assistance investigating, reach out to a Software Engineer in Test in #s_developer_experience.

Note to the merge request author and maintainer

If you have questions about the patch release process, please:

• Refer to the patch release runbook for engineers and maintainers for guidance.
• Ask questions on the #releases Slack channel (internal only).
• Once the backport has been merged, the commit changes will be automatically deployed to a release environment that can be used for manual validation. See after merging runbook for details.