Require CODEOWNERS Database section

What does this MR do and why?

Requires database approval for changes to database tagged files in CODEOWNERS per #377326. In addition to requiring database CODEOWNERS approval, we also remove the database maintainers group from the CODEOWNERS * rule.

This MR also uses the Danger config excluded_required_codeowners_sections_for_roulette introduced in gitlab-org/ruby/gems/gitlab-dangerfiles!216 (merged) to address the concerns about having two review suggestions for Database in a previous MR that attempted to require this section.

MR acceptance checklist

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