Test against the 14.0.x backups

What does this MR do?

Updates the version of the backup to be from 14.0. Migrations in newer versions will have expected that all migrations, including background migrations, from prior to 14.0 will have already been run, so we need to update our backup used in the tests to reflect that.

Related issues

Part of #2785 (closed)

How the backup was generated

• I generate the backup by running a ci pipeline for the stable branch I want a backup for, in this case 5-0-stable
• In that pipeline I cancel the qa jobs (but leave the spec tests) so that we don't get extra data in the backup
• I let the spec tests finish. They will have installed the old backup, and migrated the instance to the version we want
• Edit the gitlab-runner deployment replicas to 0, so the runner turns off
• Login to the UI and delete the runner from the admin section. (This should help avoid cipher errors later)
• Ensure the background migrations all complete, or go ahead and force them to https://docs.gitlab.com/ee/update/#checking-for-background-migrations-before-upgrading
• I bounce the task-runner pod (this is so there is no existing tmp data, in order to keep the backup small)
• I run a new backup from the bounced task-runner pod
• I download the new backup from the ci minio
• Rename and upload the backup to the proper location in our gcs

Checklist

See Definition of done.

For anything in this list which will not be completed, please provide a reason in the MR discussion.

Required

• Merge Request Title and Description are up to date, accurate, and descriptive
• MR targeting the appropriate branch
• MR has a green pipeline on GitLab.com

Expected (please provide an explanation if not completing)

• Test plan indicating conditions for success has been posted and passes
• Documentation created/updated
• Tests added
• Integration tests added to GitLab QA
• Equivalent MR/issue for omnibus-gitlab opened