Fix invalid LABEL directive

What does this MR do?

• Fixes an invalid LABEL directive to use maintainer=
• Change gitlab-{ce,ee}-qa maintainer(s) to GitLab Quality Team

Does this MR meet the acceptance criteria?

Conformity

• [-] Changelog entry
• [-] Documentation (if required)
• Code review guidelines
• Merge request performance guidelines
• Style guides
• [-] Database guides
• [-] Separation of EE specific content