Merge branch 'docs-metadata-vuln-findings' into 'master'

Docs: Add metadata to Vulnerability findings page

See merge request gitlab-org/gitlab!42042

doc/api/vulnerability_findings.md

+---
+stage: Secure
+group: Threat Insights
+info: To determine the technical writer assigned to the Stage/Group associated with this page, see https://about.gitlab.com/handbook/engineering/ux/technical-writing/#designated-technical-writers
+---
+
 # Vulnerability Findings API **(ULTIMATE)**
 
 > [Introduced](https://gitlab.com/gitlab-org/gitlab/-/merge_requests/19029) in GitLab Ultimate 12.5.