Merge branch 'docs-rules-when' into 'master'

Add rules:when entry to yaml reference

See merge request https://gitlab.com/gitlab-org/gitlab/-/merge_requests/150080



Merged-by: Lysanne Pinto <lpinto@gitlab.com>
Approved-by: Lysanne Pinto <lpinto@gitlab.com>
Co-authored-by: Marcel Amirault <mamirault@gitlab.com>