Update ownership of Invalidate Markdown Cache docs page to group::project management

What does this MR do?

Updates ownership of doc/administration/invalidate_markdown_cache.md to groupproject management per #321300 (closed)

Conflicts with !53785 (merged)

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