Fix broken docs link to triage policies

What does this MR do?

This link was invalidated after gitlab-com/www-gitlab-com@431bf966 was merged in the Handbook.

This MR rectifies the discrepancy.

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