Revert "Merge branch 'fc-show-composite-accounts-as-agents' into 'master' "

Purpose of revert

Reverts Show composite accounts as agents on work items (!216003 - merged) • Frédéric Caplette • 18.7 as this seems to be responsible for a broken master: Friday 2025-12-12 19:10 UTC - `gitlab-org/gitla... (gitlab-org/quality/engineering-productivity/master-broken-incidents#20073 - closed) • Hayley Swimelar

Checklist

• Create an issue to reinstate the merge request and assign it to the author of the reverted merge request.
• If the revert is to resolve a broken 'master' incident, please read through the Responsibilities of the Broken master resolution DRI.
• If the revert involves a database migration, please read through Deleting existing migrations.
• Add the appropriate labels before the MR is created. We can skip CI/CD jobs only if the labels are added before the CI/CD pipeline is created.

Milestone info

• I am reverting something in the current milestone. No changelog is needed, and I've added a ~"regression:*" label.
• I am reverting something in a different milestone. A changelog is needed, and I've removed the ~"regression:*" label.

Related issues and merge requests