Reenable MySQL tests on all CE and EE branches

What does this MR do?

Reenables MySQL tests on all CE and EE branches.

Are there points in the code the reviewer needs to double check?

Why was this MR needed?

Testing that is important enough to run on master should also be run on any branch before it is merged into master. The master branch should be protected from easily preventable failures.

More discussion in the issue: https://gitlab.com/gitlab-org/gitlab-ce/issues/36384

Does this MR meet the acceptance criteria?

• Changelog entry added, if necessary
• Documentation created/updated
• API support added
• Tests added for this feature/bug
• Review
  • Has been reviewed by UX
  • Has been reviewed by Frontend
  • Has been reviewed by Backend
  • Has been reviewed by Database
• Conform by the merge request performance guides
• Conform by the style guides
• Squashed related commits together

What are the relevant issue numbers?

Closes https://gitlab.com/gitlab-org/gitlab-ce/issues/36384