chore: remove unused backend-ai-agent-list (#2683)

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**Checklist:** (if applicable)

- [ ] Mention to the original issue
- [ ] Documentation
- [ ] Minium required manager version
- [ ] Specific setting for review (eg., KB link, endpoint or how to setup)
- [ ] Minimum requirements to check during review
- [ ] Test case(s) to demonstrate the difference of before/after