Merge branch 'fix-code-highlighting-for-metadata-docs' into 'master'

Fix code highlight for metadata docs

Closes #219279

See merge request gitlab-org/gitlab!33192

doc/development/documentation/index.md

@@ -76,7 +76,7 @@ For example, the following metadata would be at the beginning of a product
 documentation page whose content is primarily associated with the Audit Events
 feature:
 
-```md
+```yaml
 ---
 stage: Monitor
 group: APM