Add code owners for RuboCop files

What does this MR do?

This MR makes @gl-quality/eng-prod, @dstull, and @splattael codeowners of related RuboCop files.

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